This document summarizes information about viroids and prions. It discusses viroids, which are small circular RNA molecules that infect plants and cause disease but do not encode any proteins. The potato spindle tuber viroid is described as one of the first viroids discovered that causes potato spindle tuber disease. Prions are described as unconventional infectious agents made of misfolded protein that cause transmissible spongiform encephalopathies like mad cow disease. The document also discusses how viroids and prions were discovered and researched, as well as their structures, modes of transmission, and diseases caused.
Viroids are small, circular, non-encapsidated RNA molecules that infect plants and cause disease. They consist solely of nucleic acid and replicate autonomously using host cell machinery. Viroids range in size from 250-400 nucleotides and have various pathogenic effects on infected plants such as distorted growth and reduced yields. They replicate through rolling circle mechanisms using host RNA polymerases and can move systemically within the plant through the phloem. While most viroids only infect plants, the hepatitis delta virus is a human pathogen that requires hepatitis B for infection.
This document summarizes key information about viroids. It defines viroids as the smallest known infectious agents, consisting of small circular RNA molecules without capsids. The first viroid discovered was the potato spindle tuber viroid. Viroids are obligate parasites that replicate through a rolling circle mechanism in the nucleus of host cells. They have extensive intrastrand base pairing that allows them to avoid degradation. While viroids do not code for proteins, the hepatitis D viroid produces two RNA molecules, one that codes for the delta antigen protein. Viroids can cause economic losses through various plant diseases.
Viriods are small circular RNA molecules without a protein coat that infect plants and animals. They replicate by hijacking the host's machinery and can cause diseases like potato spindle tuber disease in plants and Hepatitis D in humans. Prions are infectious protein particles that cause neurodegenerative diseases by changing the folding of normal host proteins. Examples include scrapie in sheep and mad cow disease in cattle. They are transmitted through ingestion and cause diseases by triggering apoptosis in the brain.
This document discusses viroids, virusoids, and prions. It defines viroids as small, circular, single-stranded RNA molecules without a protein coat that can infect plants. Viroids were first reported in 1971 and the most studied is the Potato Spindle Tuber Viroid. Virusoids are also circular single-stranded RNAs that depend on plant viruses for replication and encapsidation. Prions are small infectious particles composed of abnormally folded protein that can transmit their misfolded shape to normal variants of the same protein.
Viroids are the smallest known agents of infectious disease that cause disease in plants. They are composed of short strands of circular, single-stranded RNA that can self-replicate using the host cell's machinery. In 1971, viroids were discovered by Theodor Diener who found an acellular particle that infected potato plants, causing tuber deformities. There are 30 known viroid species classified into two families based on their structure and composition. Viroids can infect a wide range of plants such as potatoes, coconut palms, avocados, and citrus trees, causing diseases marked by symptoms like stunting, chlorosis, and fruit deformities.
This document discusses the discovery and structure of viruses. It describes how Ivanovsky and Beijerinck discovered viruses through filtration experiments in the late 1800s. Viruses were found to be filterable, invisible agents that could not be grown in culture. The structure of viruses is then explained, noting they contain nucleic acids surrounded by a protein capsid, and some have an outer envelope. Viruses are much smaller than bacteria and lack cellular structures like organelles.
Animal viruses are self replicating, intracellular parasites that completely rely on host animal cell for reproduction. They use the host's cellular components to replicate, then leaves the host cell to infect other cells.
Viroids are plant pathogens composed of circular RNA molecules without protein coding capacity. They were first discovered and characterized in 1971 by Theodor Otto Diener. Viroids replicate inside plant cell nuclei using a rolling circle mechanism and then move to neighboring cells through plasmodesmata or phloem. They cause over 20 plant diseases, including potato spindle tuber disease and coconut cadang-cadang disease. Viroids are believed to trigger pathogenicity through an RNA silencing response in the host plant, leading to destruction of host mRNA and silencing of host genes.
Viroids are small, circular, non-encapsidated RNA molecules that infect plants and cause disease. They consist solely of nucleic acid and replicate autonomously using host cell machinery. Viroids range in size from 250-400 nucleotides and have various pathogenic effects on infected plants such as distorted growth and reduced yields. They replicate through rolling circle mechanisms using host RNA polymerases and can move systemically within the plant through the phloem. While most viroids only infect plants, the hepatitis delta virus is a human pathogen that requires hepatitis B for infection.
This document summarizes key information about viroids. It defines viroids as the smallest known infectious agents, consisting of small circular RNA molecules without capsids. The first viroid discovered was the potato spindle tuber viroid. Viroids are obligate parasites that replicate through a rolling circle mechanism in the nucleus of host cells. They have extensive intrastrand base pairing that allows them to avoid degradation. While viroids do not code for proteins, the hepatitis D viroid produces two RNA molecules, one that codes for the delta antigen protein. Viroids can cause economic losses through various plant diseases.
Viriods are small circular RNA molecules without a protein coat that infect plants and animals. They replicate by hijacking the host's machinery and can cause diseases like potato spindle tuber disease in plants and Hepatitis D in humans. Prions are infectious protein particles that cause neurodegenerative diseases by changing the folding of normal host proteins. Examples include scrapie in sheep and mad cow disease in cattle. They are transmitted through ingestion and cause diseases by triggering apoptosis in the brain.
This document discusses viroids, virusoids, and prions. It defines viroids as small, circular, single-stranded RNA molecules without a protein coat that can infect plants. Viroids were first reported in 1971 and the most studied is the Potato Spindle Tuber Viroid. Virusoids are also circular single-stranded RNAs that depend on plant viruses for replication and encapsidation. Prions are small infectious particles composed of abnormally folded protein that can transmit their misfolded shape to normal variants of the same protein.
Viroids are the smallest known agents of infectious disease that cause disease in plants. They are composed of short strands of circular, single-stranded RNA that can self-replicate using the host cell's machinery. In 1971, viroids were discovered by Theodor Diener who found an acellular particle that infected potato plants, causing tuber deformities. There are 30 known viroid species classified into two families based on their structure and composition. Viroids can infect a wide range of plants such as potatoes, coconut palms, avocados, and citrus trees, causing diseases marked by symptoms like stunting, chlorosis, and fruit deformities.
This document discusses the discovery and structure of viruses. It describes how Ivanovsky and Beijerinck discovered viruses through filtration experiments in the late 1800s. Viruses were found to be filterable, invisible agents that could not be grown in culture. The structure of viruses is then explained, noting they contain nucleic acids surrounded by a protein capsid, and some have an outer envelope. Viruses are much smaller than bacteria and lack cellular structures like organelles.
Animal viruses are self replicating, intracellular parasites that completely rely on host animal cell for reproduction. They use the host's cellular components to replicate, then leaves the host cell to infect other cells.
Viroids are plant pathogens composed of circular RNA molecules without protein coding capacity. They were first discovered and characterized in 1971 by Theodor Otto Diener. Viroids replicate inside plant cell nuclei using a rolling circle mechanism and then move to neighboring cells through plasmodesmata or phloem. They cause over 20 plant diseases, including potato spindle tuber disease and coconut cadang-cadang disease. Viroids are believed to trigger pathogenicity through an RNA silencing response in the host plant, leading to destruction of host mRNA and silencing of host genes.
Viroids are the smallest self-replicating pathogens known, consisting of naked circular or linear RNA without a capsid. They infect and replicate autonomously in plant cells and can cause devastating crop diseases. Prions are misfolded protein aggregates that can replicate and propagate, causing fatal neurodegenerative diseases in humans and animals. Tobacco mosaic virus was the first virus discovered and crystallized. It is a rod-shaped RNA virus that infects tobacco and other plants in the nightshade family, causing characteristic mottling and discoloration of leaves.
This document discusses viroids, prions, and phytoplasmas. It defines them as follows: viroids are small circular RNA molecules that infect plants and disrupt protein synthesis; prions are misfolded infectious proteins that cause diseases like mad cow disease; and phytoplasmas are wall-less bacteria that infect plant phloem and are transmitted by insects. It provides details on their structures, modes of infection/multiplication, and diseases caused. Control measures mentioned include breeding resistance, insect control, cryotherapy, and antibiotics.
TOBACCO MOSAIC VIRUS (Genome organization &their replication) TMV is a plant virus which infects a wide range of plants, especially tobacco and other members of the family Solanaceae and cucumbers, and a number of ornamental flowers.
This document discusses virus taxonomy and classification. It provides:
1. An overview of virus classification systems, which are primarily based on phenotypic characteristics like morphology, nucleic acid type, host, and disease symptoms.
2. A history of virus naming conventions from early systems based on host names to current standardized systems like ICTV and Baltimore classifications.
3. Details on the International Committee on Taxonomy of Viruses (ICTV) which develops agreed-upon virus taxonomy, names, and classifications communicated internationally.
Satellite viruses are small viruses that require a helper virus for replication and movement. They have their own coat protein but depend on the helper virus. There are three subgroups: 1) large messenger RNA satellites up to 1.5kb that encode proteins, 2) small linear non-coding RNAs under 800 nucleotides, and 3) small circular RNAs under 400 nucleotides. Satellite viruses modulate symptoms of helper viruses and can be developed into expression vectors.
1.INTRODUCTION
2.HISTORY
3.MORPHOLOGY
4.STRUCTURE
5.CLASSIFICATION
6.CHARACTERSTICS
7.DISEASES
8.CONCLUSION
REFRENCES
Mycoplasmas are prokaryotic , without cell wall & have been placed under the class Mollicutes & the order Mycoplasmatales.
Mycoplasma are the smallest microorganism which have been known to cause a number of disease in animals &human kind.
The cells are bounded by a soft trilamellar lipoproteinaceous unit membrane containing sterols. Because of their plasticity , they can pass through bacterial filters & have often been mistaken for viruses.
Viruses, viroids, and prions are infectious agents. Viruses contain genetic material surrounded by a protein coat and infect all domains of life. Viroids are small, circular RNA molecules that infect plants and require a host RNA polymerase for replication. Prions are composed primarily of misfolded protein and cause neurodegenerative diseases in humans and animals by inducing normal protein molecules to take on their abnormal shape.
Virus nomenclature classification and propertiessaiyam gothi
This document discusses viruses, including their definition, discovery, classification, and properties. It defines viruses as non-living particles that can only multiply within host cells. Some key points include:
- Viruses were first discovered in the late 1800s and early 1900s, including tobacco mosaic virus and viruses that cause smallpox and rabies.
- Viruses are classified based on their structure, genetic composition, and the hosts they infect, with the main systems being Baltimore classification and ICTV classification.
- Properties of viruses include their small size range of 20-350nm, that they are obligate intracellular parasites, and that they contain either RNA or DNA but not both.
This document discusses the Cauliflower Mosaic Virus (CaMV) and its potential use for gene transfer in plants. CaMV is a plant virus that infects brassica plants like cauliflower and turnips. It has a circular double-stranded DNA genome and is spherical in shape. The 35S promoter from CaMV is commonly used in plant transformation due to its strong constitutive expression in dicots. For gene transfer, foreign DNA can be inserted into the non-essential genes II or VII of CaMV. However, CaMV has limitations for gene transfer due to its limited insertion capacity and loss of infectivity if too many nucleotides are added.
A virion is the complete, infectious form of a virus outside of a host cell. It consists of a core of RNA or DNA protected by a protein capsid. Most plant viruses have a rod-shaped virion structure with a naked cylindrical capsid. While a virion infects all types of organisms, a viroid only infects plants. Key features of a virion are that it becomes inactivated when exposed to solvents like chloroform and it has an icosahedral shape with 20 triangular faces in its capsid. Both viruses and virions are non-cellular, obligate parasites that consist of DNA or RNA and can act as infectious agents in a host-specific manner.
Prions are infectious protein particles that cause fatal neurodegenerative diseases in humans and animals. Prions are composed solely of protein and lack DNA or RNA. They are the cause of transmissible spongiform encephalopathies (TSEs), diseases which destroy brain tissue and cause large vacuoles, giving the brain a spongy appearance. Prions convert normal cellular prion proteins (PrPc) into an abnormal disease-causing form (PrPsc) which aggregates to form plaques that damage brain tissue. Common symptoms of TSEs include dementia, loss of motor coordination, insomnia, and eventually death.
Mycoplasma are a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by common antibiotics like penicillin that target cell wall synthesis. Several Mycoplasma species are pathogenic in humans, including M. pneumoniae which causes atypical pneumonia and respiratory disorders, and M. genitalium and M. hominis which are associated with pelvic inflammatory disease. Mycoplasma are also the smallest bacterial cells discovered and can survive without oxygen.
TMV (Tobacco mosaic virus) is the most serious pathogen affecting tobacco plants. It causes mosaic symptoms on the leaves and stunts plant growth. TMV has a rod-shaped structure and is composed of RNA inside a protein capsid. The viral RNA directs the production of coat proteins and other proteins upon entry into host cells. TMV spreads through mechanical transmission via contact with infected plant matter and can contaminate seeds, but is not insect-transmitted. Management of TMV involves crop rotation, sanitation practices, and the use of resistant varieties.
The document discusses plant viruses. It begins by outlining learning objectives about plant virus infections, life cycles, transmission, structures, classification, replication, symptoms, identification, and control. It then provides details on the characteristics of plant viruses, including their non-cellular nature and dependence on host cells. The document discusses plant virus transmission methods, proteins, capsids, classifications, replication cycles for different types of viruses, symptoms, and methods of detection, identification, and control.
Viruses come in a variety of shapes and sizes, with the main morphological types being helical, icosahedral, prolate, enveloped, and complex. They are composed of a nucleic acid core surrounded by a protein capsid, and some have an additional outer envelope. Viruses infect all types of living organisms by introducing their genetic material inside host cells and hijacking the cells' machinery to replicate themselves.
The human immunodeficiency virus (HIV) is a retrovirus that infects and destroys CD4+ T cells of the immune system. It has an outer envelope containing glycoproteins gp120 and gp41, and an inner cone-shaped nucleocapsid enclosing two copies of positive-sense RNA and viral enzymes. HIV binds host cells via CD4 and CCR5/CXCR4 receptors, undergoes reverse transcription and integration to form proviral DNA, and hijacks the host cell to produce new virus particles that bud from the cell and infect others.
Bacteriophages, or phages, are viruses that infect bacteria. There are two main life cycles for phages: lytic and lysogenic. In the lytic cycle, the phage hijacks the bacterial cell to produce new phages then causes the cell to burst. In the lysogenic cycle, the phage inserts its DNA into the bacterial chromosome where it remains inactive until conditions trigger the lytic cycle. Phages have many applications including phage therapy to treat bacterial infections, using phage lysins as antimicrobials, and phage display to identify molecules that bind to targets of interest.
This document discusses virus classification systems. It provides an overview of the Baltimore classification system, which categorizes viruses based on their method of mRNA production. Group I viruses contain double-stranded DNA and produce mRNA through transcription. Group II viruses have single-stranded DNA and produce a double-stranded DNA intermediate before transcription. Group III viruses use double-stranded RNA, with one strand serving as the mRNA template. Group IV viruses contain single-stranded RNA with positive polarity that directly serves as mRNA.
The document summarizes key details about Tobacco Mosaic Virus (TMV), including its history, structure, and replication process. It notes that TMV was the first virus to be purified and shown to consist of protein and nucleic acid. Studies in the 1930s-1940s revealed that TMV has a rod-shaped structure consisting of a protein coat containing a single strand of RNA. The RNA acts as a template for the virus to replicate by synthesizing more copies of itself within the host plant cell. TMV remains an important model system for understanding viral structure and replication.
Oncogenic viruses can induce cancer by integrating their genetic material into the host cell's DNA. This can activate oncogenes and transform normal cells into cancerous cells. Prions are infectious proteins that cause neurodegenerative diseases by converting the normal form of the prion protein into an abnormal configuration. Viruses can be treated through vaccines containing attenuated viruses to stimulate immunity without causing illness, as well as antiviral drugs that inhibit viral replication.
Basics microbiology, that have as learning objective: Differentiate a virus from a bacterium. Characteristics about viruses. (Des Moines Area Community College´s PPT File)
Viroids are the smallest self-replicating pathogens known, consisting of naked circular or linear RNA without a capsid. They infect and replicate autonomously in plant cells and can cause devastating crop diseases. Prions are misfolded protein aggregates that can replicate and propagate, causing fatal neurodegenerative diseases in humans and animals. Tobacco mosaic virus was the first virus discovered and crystallized. It is a rod-shaped RNA virus that infects tobacco and other plants in the nightshade family, causing characteristic mottling and discoloration of leaves.
This document discusses viroids, prions, and phytoplasmas. It defines them as follows: viroids are small circular RNA molecules that infect plants and disrupt protein synthesis; prions are misfolded infectious proteins that cause diseases like mad cow disease; and phytoplasmas are wall-less bacteria that infect plant phloem and are transmitted by insects. It provides details on their structures, modes of infection/multiplication, and diseases caused. Control measures mentioned include breeding resistance, insect control, cryotherapy, and antibiotics.
TOBACCO MOSAIC VIRUS (Genome organization &their replication) TMV is a plant virus which infects a wide range of plants, especially tobacco and other members of the family Solanaceae and cucumbers, and a number of ornamental flowers.
This document discusses virus taxonomy and classification. It provides:
1. An overview of virus classification systems, which are primarily based on phenotypic characteristics like morphology, nucleic acid type, host, and disease symptoms.
2. A history of virus naming conventions from early systems based on host names to current standardized systems like ICTV and Baltimore classifications.
3. Details on the International Committee on Taxonomy of Viruses (ICTV) which develops agreed-upon virus taxonomy, names, and classifications communicated internationally.
Satellite viruses are small viruses that require a helper virus for replication and movement. They have their own coat protein but depend on the helper virus. There are three subgroups: 1) large messenger RNA satellites up to 1.5kb that encode proteins, 2) small linear non-coding RNAs under 800 nucleotides, and 3) small circular RNAs under 400 nucleotides. Satellite viruses modulate symptoms of helper viruses and can be developed into expression vectors.
1.INTRODUCTION
2.HISTORY
3.MORPHOLOGY
4.STRUCTURE
5.CLASSIFICATION
6.CHARACTERSTICS
7.DISEASES
8.CONCLUSION
REFRENCES
Mycoplasmas are prokaryotic , without cell wall & have been placed under the class Mollicutes & the order Mycoplasmatales.
Mycoplasma are the smallest microorganism which have been known to cause a number of disease in animals &human kind.
The cells are bounded by a soft trilamellar lipoproteinaceous unit membrane containing sterols. Because of their plasticity , they can pass through bacterial filters & have often been mistaken for viruses.
Viruses, viroids, and prions are infectious agents. Viruses contain genetic material surrounded by a protein coat and infect all domains of life. Viroids are small, circular RNA molecules that infect plants and require a host RNA polymerase for replication. Prions are composed primarily of misfolded protein and cause neurodegenerative diseases in humans and animals by inducing normal protein molecules to take on their abnormal shape.
Virus nomenclature classification and propertiessaiyam gothi
This document discusses viruses, including their definition, discovery, classification, and properties. It defines viruses as non-living particles that can only multiply within host cells. Some key points include:
- Viruses were first discovered in the late 1800s and early 1900s, including tobacco mosaic virus and viruses that cause smallpox and rabies.
- Viruses are classified based on their structure, genetic composition, and the hosts they infect, with the main systems being Baltimore classification and ICTV classification.
- Properties of viruses include their small size range of 20-350nm, that they are obligate intracellular parasites, and that they contain either RNA or DNA but not both.
This document discusses the Cauliflower Mosaic Virus (CaMV) and its potential use for gene transfer in plants. CaMV is a plant virus that infects brassica plants like cauliflower and turnips. It has a circular double-stranded DNA genome and is spherical in shape. The 35S promoter from CaMV is commonly used in plant transformation due to its strong constitutive expression in dicots. For gene transfer, foreign DNA can be inserted into the non-essential genes II or VII of CaMV. However, CaMV has limitations for gene transfer due to its limited insertion capacity and loss of infectivity if too many nucleotides are added.
A virion is the complete, infectious form of a virus outside of a host cell. It consists of a core of RNA or DNA protected by a protein capsid. Most plant viruses have a rod-shaped virion structure with a naked cylindrical capsid. While a virion infects all types of organisms, a viroid only infects plants. Key features of a virion are that it becomes inactivated when exposed to solvents like chloroform and it has an icosahedral shape with 20 triangular faces in its capsid. Both viruses and virions are non-cellular, obligate parasites that consist of DNA or RNA and can act as infectious agents in a host-specific manner.
Prions are infectious protein particles that cause fatal neurodegenerative diseases in humans and animals. Prions are composed solely of protein and lack DNA or RNA. They are the cause of transmissible spongiform encephalopathies (TSEs), diseases which destroy brain tissue and cause large vacuoles, giving the brain a spongy appearance. Prions convert normal cellular prion proteins (PrPc) into an abnormal disease-causing form (PrPsc) which aggregates to form plaques that damage brain tissue. Common symptoms of TSEs include dementia, loss of motor coordination, insomnia, and eventually death.
Mycoplasma are a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by common antibiotics like penicillin that target cell wall synthesis. Several Mycoplasma species are pathogenic in humans, including M. pneumoniae which causes atypical pneumonia and respiratory disorders, and M. genitalium and M. hominis which are associated with pelvic inflammatory disease. Mycoplasma are also the smallest bacterial cells discovered and can survive without oxygen.
TMV (Tobacco mosaic virus) is the most serious pathogen affecting tobacco plants. It causes mosaic symptoms on the leaves and stunts plant growth. TMV has a rod-shaped structure and is composed of RNA inside a protein capsid. The viral RNA directs the production of coat proteins and other proteins upon entry into host cells. TMV spreads through mechanical transmission via contact with infected plant matter and can contaminate seeds, but is not insect-transmitted. Management of TMV involves crop rotation, sanitation practices, and the use of resistant varieties.
The document discusses plant viruses. It begins by outlining learning objectives about plant virus infections, life cycles, transmission, structures, classification, replication, symptoms, identification, and control. It then provides details on the characteristics of plant viruses, including their non-cellular nature and dependence on host cells. The document discusses plant virus transmission methods, proteins, capsids, classifications, replication cycles for different types of viruses, symptoms, and methods of detection, identification, and control.
Viruses come in a variety of shapes and sizes, with the main morphological types being helical, icosahedral, prolate, enveloped, and complex. They are composed of a nucleic acid core surrounded by a protein capsid, and some have an additional outer envelope. Viruses infect all types of living organisms by introducing their genetic material inside host cells and hijacking the cells' machinery to replicate themselves.
The human immunodeficiency virus (HIV) is a retrovirus that infects and destroys CD4+ T cells of the immune system. It has an outer envelope containing glycoproteins gp120 and gp41, and an inner cone-shaped nucleocapsid enclosing two copies of positive-sense RNA and viral enzymes. HIV binds host cells via CD4 and CCR5/CXCR4 receptors, undergoes reverse transcription and integration to form proviral DNA, and hijacks the host cell to produce new virus particles that bud from the cell and infect others.
Bacteriophages, or phages, are viruses that infect bacteria. There are two main life cycles for phages: lytic and lysogenic. In the lytic cycle, the phage hijacks the bacterial cell to produce new phages then causes the cell to burst. In the lysogenic cycle, the phage inserts its DNA into the bacterial chromosome where it remains inactive until conditions trigger the lytic cycle. Phages have many applications including phage therapy to treat bacterial infections, using phage lysins as antimicrobials, and phage display to identify molecules that bind to targets of interest.
This document discusses virus classification systems. It provides an overview of the Baltimore classification system, which categorizes viruses based on their method of mRNA production. Group I viruses contain double-stranded DNA and produce mRNA through transcription. Group II viruses have single-stranded DNA and produce a double-stranded DNA intermediate before transcription. Group III viruses use double-stranded RNA, with one strand serving as the mRNA template. Group IV viruses contain single-stranded RNA with positive polarity that directly serves as mRNA.
The document summarizes key details about Tobacco Mosaic Virus (TMV), including its history, structure, and replication process. It notes that TMV was the first virus to be purified and shown to consist of protein and nucleic acid. Studies in the 1930s-1940s revealed that TMV has a rod-shaped structure consisting of a protein coat containing a single strand of RNA. The RNA acts as a template for the virus to replicate by synthesizing more copies of itself within the host plant cell. TMV remains an important model system for understanding viral structure and replication.
Oncogenic viruses can induce cancer by integrating their genetic material into the host cell's DNA. This can activate oncogenes and transform normal cells into cancerous cells. Prions are infectious proteins that cause neurodegenerative diseases by converting the normal form of the prion protein into an abnormal configuration. Viruses can be treated through vaccines containing attenuated viruses to stimulate immunity without causing illness, as well as antiviral drugs that inhibit viral replication.
Basics microbiology, that have as learning objective: Differentiate a virus from a bacterium. Characteristics about viruses. (Des Moines Area Community College´s PPT File)
Prions are infectious agents that are composed of misfolded protein aggregates called PrP, lacking nucleic acid. They can cause fatal neurodegenerative diseases in humans and animals by converting normal PrP proteins into additional misfolded prions. Common prion diseases include Creutzfeldt-Jakob disease in humans, mad cow disease in cattle, and scrapie in sheep. Prions are highly resistant to sterilization by heat, chemicals, radiation, and are difficult to inactivate.
Proteins are fundamental components of living cells and come in many forms like hemoglobin, hormones, antibodies, enzymes, and structural proteins. Proteins have a primary structure defined by their amino acid sequence and commonly form secondary structures like alpha helices and beta sheets. For a protein to function properly it must fold into its correct three-dimensional tertiary structure. Misfolded proteins can aggregate and poison cells. Prions are abnormal infectious protein particles that cause neurodegenerative diseases by converting normal cellular prion proteins into the abnormal misfolded prion form.
- In the 1950s, a disease called kuru was observed among the Fore people of New Guinea that caused trembling, loss of motor control, and ultimately death.
- Kuru and other transmissible spongiform encephalopathies (TSEs) are caused by prion proteins, which are unique infectious proteins that can reproduce on their own and convert normal prion proteins into the abnormal infectious form.
- Prions are extremely resistant to heat and chemicals and can survive in the environment for many years. They infect the central nervous system and cause neurodegeneration through a chain reaction that multiplies copies of the infectious prion protein.
The document summarizes audience feedback from a test screening of a film opening sequence. Viewers felt that with some improvements, the sequence showed potential to be an effective opening. Suggested enhancements included adding titles to establish it as an opening, finishing visual effects, improving editing in certain scenes, and providing more context with a background for a news report section. Strengths mentioned were good acting, costumes, and atmosphere created by scene switching.
Viruses are different from other kingdoms in that they are not cells, are extremely small and unable to move, and cannot carry out vital functions without infecting a host cell. Viruses have either nucleic acid or nucleic acid surrounded by a protein capsid, and sometimes an envelope. To reproduce, viruses enter a host cell and use its cellular machinery to make new viral components which then assemble and exit the cell.
Virions are complete virus particles that contain genetic material (DNA or RNA), a protein capsid, and sometimes an envelope. They are found outside cells and can infect both cells and organisms. Virioids, in contrast, are small circular RNA molecules that do not encode proteins but can replicate autonomously in plant cells, inducing disease. Unlike virions, virioids do not have a protein coat and are much smaller, infect only plants, and move between cells via plasmodesmata or long-distance through the phloem. The key differences are that virions contain DNA or RNA and a protein coat while virioids are naked RNA, and virions can infect all organisms while virioids exclusively infect
Viruses are non-living particles that can only replicate inside host cells. They contain genetic material surrounded by a protein coat. While viruses exhibit some properties of life, such as the ability to evolve, they cannot perform all biological functions or maintain homeostasis. Viruses come in a variety of shapes and sizes and infect organisms as diverse as plants, animals, bacteria and archaea. They are classified according to their nucleic acid composition and structure. Viruses either enter a dormant latent stage within the host cell or undergo lytic replication, which results in host cell death. Treatment options for viral diseases include vaccines containing weakened live or killed viruses, interferons, antiviral drugs that target specific virus functions, and genetic engineering of attenuated viruses
Biopolymers are polymers produced by living organisms. Degradation is the process by which large polymers are fragmented into smaller molecules. There are several types of degradation including thermal, photo, mechanical, chemical, and oxidative. Biodegradation is the natural process by which organic chemicals are converted into simpler compounds by organisms like fungi and bacteria. The degradation mechanisms of some common biopolymers like starch, cellulose, poly(caprolactone), and poly(lactic acid) are discussed. Enzymes play an important role in degradation through processes like hydrolysis which breaks the polymer chains into monomers.
Red biotechnologies, which include areas like pharmaceuticals and healthcare, currently make up 60% of biotech usage. Biotechnology has many branches including bioengineering, biomedicine, nanomedicine, and bioinformatics. Some key innovations in biotechnology that will impact humanity include using genetically modified corn to help feed people in third world countries, creating biofuels from marine resources and fungi, and advancing regenerative medicine to grow new organs. Personalized and fast diagnosis, as well as improving healthcare through genomics, are also areas that biotechnology is making strides.
Prions are proteinaceous infectious particles that lack nucleic acid and cause fatal neurodegenerative diseases. They exist in two forms - a normal cellular form (PrPc) and an abnormal disease-causing form (PrPsc). PrPsc has a different structure than PrPc which allows it to accumulate and convert PrPc into more PrPsc, ultimately causing neuropathology. Prion diseases affect both humans and animals and manifest as infectious, genetic, and sporadic disorders with varied clinical presentations. Common features include neurological deficits, dementia, and spongiform changes in the brain. Prions are extremely resistant to decomposition and differ from bacteria and viruses by being protein-only entities that propagate through conversion of
Applications of environmental biotechnology by Hameer KhanHumair Sindhi
The document discusses applications of environmental biotechnology. It defines environmental biotechnology as using biological systems to develop and regulate the environment in a sustainable way. It discusses six major applications: biomarkers to measure pollution exposure; biosensors to detect toxins; biofuels as renewable energy; bioremediation to clean pollution; biotransformation to convert toxins; and molecular ecology to study biodiversity. Overall, environmental biotechnology aims to keep the environment clean for future generations through sustainable use of organisms.
Prion diseases are rare neurodegenerative disorders caused by misfolded prion proteins. They affect both humans and animals. In cattle it is known as bovine spongiform encephalopathy (BSE) or "mad cow disease", and in humans it is known as Creutzfeldt-Jakob disease (CJD). Prion diseases occur when normal prion proteins misfold and induce other prion proteins to also misfold, triggering a chain reaction that causes damage to neural cells. There is no cure for prion diseases and diagnosis is difficult since prion proteins are similar to normal forms.
The document discusses different types of microscopes used to view very small objects. It compares light microscopes and electron microscopes. Electron microscopes use beams of electrons instead of light to form higher magnification and resolution images. There are two main types - scanning electron microscopes, which view surface features, and transmission electron microscopes, which can view inside thin specimens at up to 500,000x magnification. Electron microscopes require specimens to be prepared differently and have more complex components than light microscopes to generate and control the electron beam.
Biotechnology is an indigenous wave of innovation. This enhances the quality of the environment by protecting the natural resources. It plays key role for sustainable agriculture.
There are several methods for composting organic waste materials. The Indore method involves filling pits layered with dry waste, cattle dung, soil, and ash. The materials are turned three times over 2-3 months for aeration and decomposition. The Bangalore method fills pits without turning for 8-9 months of decomposition. The NADEP method facilitates composting with minimum cattle dung use through aerobic decomposition. The Coimbatore method uses pits layered with waste, cattle dung suspension, and bone meal, left undisturbed for 8-10 weeks before shaping into a heap.
This document discusses environmental biotechnology and its applications. Environmental biotechnology uses biological processes like bioremediation, biosensors, and bioindicators to solve environmental problems and reduce pollution. It deals with decontaminating the environment from various contaminants released by industry, and minimizing waste and pollution through techniques like bioremediation, which uses microorganisms to degrade contaminants into less toxic forms. The document also describes different types of biosensors and bioindicators that can be used for biotechnological applications like monitoring the environment.
This document summarizes biodegradation of various xenobiotics including hydrocarbons, plastics, and pesticides. It discusses that xenobiotics are man-made chemicals that do not occur naturally. Biodegradation is the breakdown of these substances by microorganisms. Various microbes can degrade hydrocarbons through aerobic and anaerobic pathways. Plastics are broken down through hydrolysis and further degraded by acidogenic, acetogenic, and methanogenic bacteria. Pesticides are degraded through methods like dehalogenation, deamination, and hydroxylation. The document provides examples of microbes and mechanisms involved in the biodegradation of these pollutants.
Viruses are found wherever there is life and have probably existed since living cells first evolved. There are millions of different types of viruses, although only about 5,000 types have been described in detail. There are more than 219 virus species that are known to be able to infect humans. The document then provides a history of early developments in virology including discoveries by Louis Pasteur, Robert Koch, Edward Jenner, Dmitry Ivanovsky, Martinus Beijerinck, and others. It discusses the structure, composition and classification of viruses.
The document provides information about viruses including their structure, classification, life cycles, and how they cause disease. It begins by describing the characteristics of viruses and explaining that they are not living or nonliving but exhibit traits of both. It then discusses the discovery of viruses and describes the structures of representative viruses like bacteriophage, influenza, and HIV. The modes of viral classification including Baltimore classification are explained. The document also covers the parasitic nature of viruses and how they depend on host cells for replication and survival. It describes the general steps in the viral life cycle including adsorption, penetration, replication, assembly and release. The lytic and lysogenic cycles of bacteriophages are explained in detail.
This document describes the characteristics, structure, replication process, and roles of viruses. It defines viruses as extremely small agents that are not living cells and can only replicate inside host cells. Viruses contain nucleic acids surrounded by protein coats and come in different shapes. The document outlines the history of virus discovery and explains the lytic and lysogenic replication cycles that viruses use to infect host cells and produce more viruses. It also discusses the classification of viruses based on their hosts, examples of viral diseases in animals, plants and humans, and some uses of viruses in research and vaccine development.
This document discusses viroids, virusoids, and prions - three types of acellular infectious agents. It notes that viroids are small, circular RNA molecules that can self-replicate and cause diseases in plants. Virusoids are subviral RNAs that require a helper virus to replicate and infect plants. Prions are misfolded protein particles that can induce normal proteins to also misfold, leading to neurodegenerative diseases like Creutzfeldt-Jakob disease in humans and scrapie in sheep. Unlike viruses and viroids, prions contain no nucleic acid and are extremely resistant to destruction.
This document discusses viroids, virusoids, and prions - three types of acellular infectious agents. It notes that viroids are small, circular RNA molecules that can self-replicate and cause diseases in plants. Virusoids are subviral RNAs that require a helper virus to replicate and infect plants. Prions are misfolded protein particles that can induce normal proteins to also misfold, leading to neurodegenerative diseases like Creutzfeldt-Jakob disease in humans and scrapie in sheep. Unlike viruses and viroids, prions contain no nucleic acid and are extremely resistant to destruction.
viruses_tobacco mosaic virus First semester part_1UsmanKhan728
1. Viruses are non-living infectious agents that can only replicate inside host cells. They contain genetic material in the form of DNA or RNA surrounded by a protein coat.
2. Early experiments in the late 19th century demonstrated that certain disease-causing agents could be transmitted between hosts and passed through filters, establishing the existence of viruses.
3. Viruses come in a variety of shapes and sizes but are generally quite small, usually between 20-300 nanometers. Their structure includes a nucleic acid core and protein coat called a capsid, which is composed of repeating protein subunits called capsomeres.
Viroids and prions are both infectious particles but differ in their composition and effects. Viroids are sub-viral RNA particles that infect plants and lack protein coats. They are the smallest known pathogen and can cause diseases like potato tuber spindle disease. Prions are misfolded protein particles that cause neurodegenerative diseases in mammals. They were first discovered to cause scrapie in sheep and have no nucleic acids. Unlike viroids which mainly affect plants, prions cause diseases like mad cow disease and Creutzfeldt-Jakob disease in animals. There are currently no treatments for prion diseases while traditional methods are used for viroid infections.
This document provides an overview of viruses and their classification. It discusses that viruses consist of nucleic acid in a protein coat and can only reproduce within living host cells. Viruses vary in size and shape. The document then covers the discovery of viruses and their distinctive properties compared to living cells. It discusses the nomenclature and classification of viruses, including how they are classified based on their genome, structure, and hosts. Classification systems discussed include the LHT and Baltimore systems.
Bacterial virus (Bacteriophage).
Structure of bacteriophage.
Where we can find phage?
Families of bacteriophage.
Life cycle of bacteriophage.
Potential uses of bacteriophage.
Bacteriophage vs. antibiotics.
Factors affecting phage therapy.
Viruses were first discovered in the late 1880s through experiments with tobacco mosaic virus. Since then, many other viruses have been discovered that infect plants, animals and bacteria. Viruses are generally too small to be seen with a light microscope and have a variety of structures depending on their nucleic acid content and presence of an envelope. They replicate by infiltrating a host cell and using the cell's machinery to produce more viral particles. There is ongoing debate about whether viruses are considered living organisms.
Viruses were first discovered in the late 1880s through experiments with tobacco mosaic virus. Since then, many other viruses have been discovered that infect plants, animals and bacteria. Viruses are generally too small to be seen with a light microscope and have a variety of structures depending on their nucleic acid content and presence of an envelope. They replicate by infiltrating a host cell and using the cell's machinery to produce more viral particles. There is ongoing debate about whether viruses are considered living organisms.
Smallpox was intentionally spread among Native American tribes in the 18th century by distributing blankets exposed to smallpox. The disease devastated populations who had no immunity. In the late 20th century, smallpox was developed as an aerosol biological weapon by the Soviet Union. It remains a potential bioterrorism threat. Smallpox is caused by the variola virus and is highly contagious and potentially fatal if left untreated. It was declared eradicated worldwide in 1980 after global vaccination campaigns.
Viruses and Viroids - Is There A Difference.pdfVerne Bio
A virus is an infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat. Viroids can impact a number of crop plants, including cannabis and hemp plants. Having the ability to test for viruses and viroids in the palm of your hand is possible with kits from Verne BioAnalytics. Using the I-Test and W-Test kits, growers can test their crops throughout the plant’s life cycle.
Visit: https://vernebio.com/
Christ University's mission is to provide a nurturing environment for students' holistic development so they can contribute effectively to society. Its vision is excellence and service, and its core values are faith in God, moral uprightness, love for others, social responsibility, and pursuit of excellence. Viruses are the smallest and simplest known organisms, consisting of genetic material covered by a protein coat, and requiring a living host cell to replicate by using the host's cellular machinery. They cause infectious diseases in plants, animals and humans.
Virology is the study of viruses, which are small particles that can only replicate inside living cells. Viruses are non-cellular and contain either DNA or RNA as their genetic material. They have capsids made of protein that surround their genomes and allow them to attach to and enter host cells. Viruses come in different shapes determined by the symmetry of their capsids, and some have envelopes containing glycoproteins. They are transmitted through various routes like direct contact, ingestion, inhalation, or mother-to-child. Viruses can be inactivated by physical means like heat and chemical treatments, though some may be resistant to certain solvents and disinfectants depending on their structure.
This document discusses a quiz with multiple choice questions and answers about various topics. It includes 10 questions about subjects like the origins of brand names, famous people, historical events, and more. For each question, the correct answer is provided. The quiz tests a range of general knowledge topics through multiple choice format.
This document provides guidance on effective participation in a group discussion. It outlines the key skills needed like communication, listening, and body language. Some benefits of group discussions are stimulating new ways of thinking, expanding knowledge, and revealing one's true personality. The document advises making original points and supporting them with reasoning, listening actively to others, speaking with logic and examples, and avoiding interruptions or stubbornness. Proper preparation and practice are suggested.
Android is an open source operating system based on Linux that was developed for touchscreen mobile devices like smartphones and tablets. It was created by Android Inc, which was later acquired by Google in 2005. The first Android phone went on sale in October 2008.
Tropical deciduous forests are found in tropical areas with distinct wet and dry seasons. During the dry season, the trees lose their leaves but are able to regrow them when the rains return. These forests have thicker barked trees that are not as tall as rainforest trees and have sparser canopies that allow more light to reach the diverse undergrowth below. They provide habitat for a variety of animals including monkeys, tigers, birds, and reptiles that have adapted to the forest's seasonal changes. Thorny scrublands with short, thick-leaved plants replace the forests in areas with less than 70cm of annual rainfall.
Although debate formats vary around the world, most have some common characteristics:
- They focus on a fixed topic to discuss or argue
- Participants try to persuade the audience or judge of their position
- Successful arguments are supported by reasoning and evidence, while refuting opposing arguments promotes a direct clash of perspectives that is important for debate.
Melanocyte-stimulating hormone (MSH) is a group of hormones produced by the pituitary gland, hypothalamus, and skin cells in response to ultraviolet radiation. It plays a key role in producing skin, hair, and eye color by inducing melanocytes to produce melanin, which protects cells from UV-induced DNA damage and skin cancer. In some animals like frogs, MSH production increases in dark locations, causing skin darkening for camouflage from predators. MSH levels rise after UV exposure and stimulate melanocytes to make melanin, which transfers to skin cells forming caps over nuclei to shield DNA from UV damage.
This document describes a C++ program that calculates employee wages. It contains sections for acknowledgements, introduction, system requirements, source code, output, and conclusions. The program allows the user to enter information for multiple employees, including name, phone number, hours worked, and hourly wage. It then calculates and displays each employee's pay for the week. The program uses arrays to store employee data and functions for the menu, data entry, and report display.
Subrahmanyan Chandrasekhar was an Indian-American astrophysicist who won the 1983 Nobel Prize in Physics for his work on stellar structure and evolution. His most notable work calculated the maximum mass of a white dwarf star, known as the Chandrasekhar limit, which he determined to be approximately 1.44 solar masses. This limit describes the threshold above which a star will collapse into a neutron star or black hole rather than remaining a white dwarf. Chandrasekhar made this seminal calculation in 1930 and contributed significantly to the understanding of stellar evolution and late stage massive stars.
Walmart Business+ and Spark Good for Nonprofits.pdfTechSoup
"Learn about all the ways Walmart supports nonprofit organizations.
You will hear from Liz Willett, the Head of Nonprofits, and hear about what Walmart is doing to help nonprofits, including Walmart Business and Spark Good. Walmart Business+ is a new offer for nonprofits that offers discounts and also streamlines nonprofits order and expense tracking, saving time and money.
The webinar may also give some examples on how nonprofits can best leverage Walmart Business+.
The event will cover the following::
Walmart Business + (https://business.walmart.com/plus) is a new shopping experience for nonprofits, schools, and local business customers that connects an exclusive online shopping experience to stores. Benefits include free delivery and shipping, a 'Spend Analytics” feature, special discounts, deals and tax-exempt shopping.
Special TechSoup offer for a free 180 days membership, and up to $150 in discounts on eligible orders.
Spark Good (walmart.com/sparkgood) is a charitable platform that enables nonprofits to receive donations directly from customers and associates.
Answers about how you can do more with Walmart!"
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
Exploiting Artificial Intelligence for Empowering Researchers and Faculty,
International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
By Dr. Vinod Kumar Kanvaria
How to Setup Warehouse & Location in Odoo 17 InventoryCeline George
In this slide, we'll explore how to set up warehouses and locations in Odoo 17 Inventory. This will help us manage our stock effectively, track inventory levels, and streamline warehouse operations.
This presentation was provided by Steph Pollock of The American Psychological Association’s Journals Program, and Damita Snow, of The American Society of Civil Engineers (ASCE), for the initial session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session One: 'Setting Expectations: a DEIA Primer,' was held June 6, 2024.
Strategies for Effective Upskilling is a presentation by Chinwendu Peace in a Your Skill Boost Masterclass organisation by the Excellence Foundation for South Sudan on 08th and 09th June 2024 from 1 PM to 3 PM on each day.
2. Page2
Acknowledgement
At the outset, we would like to express our sincere gratitude to our school, for providing us
with such an opportunity toshowcaseour skills, our teachers for their guidance; and to each
and every one who contributed to making this project a reality. Above all, we would like to
thank God theAlmighty for giving us the strength and endurance to undertaken this project
and execute it to the best of our abilities.
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3. Page3
CONTENTS
Sl. No TOPIC Page No.
1 Abstract 5
2 Introduction 7
3 Viroid the Plant Invaders 8
4 Spindle Tuber Disease of Potato 10
5 Prion 14
6 Bovine Spongiform Encephalopathy 15
7 Bibliography 18
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4. Page4
LIST OF FIGURES
Sl. No Description Page No.
1 Dmitri Iwanowsky 5
2 Tobacco mosaic disease 5
3 Examples of Viroids 8
4 Timeline of Discovery of Viroids 9
5 Potato Spindle Tuber Disease 10
___________
LIST OF TABLES
Sl. No Description Page No.
1 Differences Between Bacteria & Viruses 7
2 Comparison of Cows’ Brain 16
___________
ABBREVIATIONS USED
Sl. No Abbreviation Abbreviated Word Page No.
1 PLMVd Pelamoviroids 8
2 ASBVd Avsunviroids 8
3 CBVd Coleviroids 8
4 PSTVd Potato Spindle Tuber Viroid 9
5 BSE Bovine Spongiform Encephalopathy
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5. Page5
ABSTRACT
Viruses are too small to be seen with a light microscope and cannot be cultured outside their
hosts. Therefore, although viraldiseases arenot new, theviruses themselves could notbestudied
until the twentieth century. In 1886, the Dutch chemist Adolf Mayer showed that tobacco
mosaic disease (TMD) was transmissiblefroma diseased plant toa healthy plant. In 1892, in an
attempt to isolate the cause of TMD, the Russian bacteriologist Dmitri Iwanowsky filtered the
sap of diseased plants through a porcelain filter that was designed to retain bacteria. He
expected to find the microbe trapped in the filter; instead, he found that the infectious agent
had passed through the minute pores of the filter. When he infected healthy plants with the
filtered fluid, they contracted TMD. The first human
diseaseassociated with a filterableagent was yellowfever.
Advances in the molecular biological techniques in the
1980s and 1990s led to the recognition of several new
viruses, including human immunodeficiency virus (HIV)
and SARS associated corona virus. Israeli acute paralysis
virus becamea concern in 2006, when it killed up to90%
of the pollinating bees in some U.S. hives. This new virus
was first seen in bees in Israel in 2002 and seems to have
been in theUnited States sincethen.
Viroids are nucleic acid species of
low molecular weight and unique
structure that cause several
important diseases of cultivated
plants. Viroids are the smallest
known agents of infectious disease.
Unlikeviral nucleic acids,
Figure 1: Dmitri Iwanowsky
Figure 2 : Tobacco mosaic disease
6. Page6
Viroids arenot encapsulated. Despitetheir smallsize, Viroids replicateautonomously in cells of
susceptibleplant species. Known Viroids aresingle-stranded, covalently closed, circular, as well
as linear, RNA molecules with extensive regions of intramolecularcomplementarily; they exist
in their native state as highly base-paired rods. The biological properties of Viroids are
determined by their primary structures; Viroids thus constitute genetic systems of minimal
complexity. Sofar, Viroids havebeen identified only as pathogens of higherplants, but it is likely
that certain animal(including human) diseases arecaused by similar agents.
Prions are unconventional infectious agents responsible for transmissible spongiform
encephalopathy (TSE) diseases. They are thought to be composed exclusively of the protease-
resistant prion protein (PrPres) that replicates in the body by inducing the misfolding of the
cellular prion protein (PrPC). Although compelling evidence supports this hypothesis,
generation of infectious prion particles in vitro has not been convincingly demonstrated. Here
we show that PrPC --> PrPres conversion can be mimicked in vitro by cyclic amplification of
protein misfolding, resultingin indefiniteamplificationof PrPres. Thein vitro-generated forms
of PrPres share similar biochemical and structural properties with PrPres derived from sick
brains. Inoculationof wild-typehamsters with in vitro-produced PrPres led toa scrapiedisease
identical to the illness produced by brain infectious material. These findings demonstrate
that prions can be generated in vitro and provide strong evidence in support of the protein-
only hypothesis of prion transmission.
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7. Page7
INTRODUCTION
One hundred years ago, researchers could not imaginesubmicroscopic particles, and thus
they described theinfectious agent as contagiumvivumfluidum—a contagious fluid. By the
1930s, scientists had begunusing theword virus, theLatin word for poison, to describethese
filterableagents. Thenatureof viruses, however, remained elusive until1935, when Wendell
Stanley, an American chemist, isolated tobaccomosaic virus, making it possible for the first
time to carry out chemicaland structuralstudies on a purified virus. At about the same time,
theinvention of the electron microscopemade it possible to see viruses.
Life can be defined as a complex set of processes resulting fromtheactions of proteins
specified by nucleic acids. Thenucleic acids of living cells are in action all thetime. Because
viruses are inert outsideliving host cells, in this sense they are not considered to be living
organisms. However, once viruses enter a host cell, the viral nucleic acids becomeactive, and
viral multiplication results. In this sense, viruses are alive when they multiply in the host cells
they infect. From a clinicalpoint of view, viruses can be considered alive becausethey cause
infection and disease, just as pathogenicbacteria, fungiand protozoa do. Depending on one’s
viewpoint, a virus may be regarded as an exceptionally complex aggregation of nonliving
chemicals, or as an exceptionally simple living microorganism.
Table 1 : Differences Between Bacteria &
VirusesViruses were originally
distinguished from other infectious
agents because they are especially
small (filterable) and because they
are obligatory intracellular
parasites—that is, they absolutely
require living host cells in order to
multiply. However, certain small
bacteria, such as some rickettsias,
share both of these properties.
Viruses and bacteria are compared
in Table 1.
8. Page8
VIROIDS - the Plant Invaders
A Viroid is a virus (VIR) like (OID) particle. Viroids are“sub-viruses” composed exclusively of
a single circularstrandof nucleic acid (RNA) that codes for a singleprotein or small, circular
RNA molecules without a protein coat.
No coding capacity - do not programtheir
own polymerase.
Use host-encoded polymerasefor
replication.
Mechanically transmitted;often seed
transmitted.
More than 40 viroid species and many
variants havebeen characterized.
“Classical” Viroids have been found only in
plants.
Viroids differ from viruses in that viruses, at
their most basic level, consist of genetic
material (DNA or RNA) contained within a
protective protein shell.
Viroids differ from prions, another typeof
sub viral infectious agent, in that prions are
made only of protein lacking nucleic acid.
DID YOU KNOW?
VIROIDS are
Very small, covalently
closed, circularRNA
molecules capableof
autonomous replication and
induction of disease.
Rangein size from
approximately 20 nm.
Are infectious particles.
Causecertain plant and
human diseases.
It consists only of Nucleic
Acid (RNA).
The smallest viroid identified so far is
a 220-nucleobase scRNA (small
cytoplasmic RNA) associated with the
rice yellow mottle sobemovirus
(RYMV) (Collins et al. 1998).
In comparison, the genomes of the
smallest known viruses capable of
causing an infection by themselves
are around two kilobases in size.
Figure 3 : Examples of Viroids
Genus Coleviroids:
CbVd 1 (coleusblumei 1)
Genus Avsunviroids:
ASBVd (avocado sunblotch)
Genus Pelamoviroids:
PLMVd (peach latent mosaic)
9. Page9
1974:
Confirmation
that Viroids
are non-
coding.
1973:
Electron
micrograph
shows Viroid’s
hairpin
structure
Discovery
Early 1960s:
Raymer and
O’Brien
develop a
bioassay for
the agent
causing potato
spindle tuber
disease. 1965:
Raymer
teams up
with Diener;
they show
that agent is
not a typical
Viroid.
1971:
Diener
demonstrate
s that the
agent is a
free non-
coding RNA,
coins the
term Viroid.
1968:
Characterization
of
chrysanthemum
stunt and citrus
exocortis as non-
typical viruses.
1978: PSTVd
is sequenced.
1976: EM
shows that
viroids
form
closed
circular
RNAs
Theodore O. Diener
Figure 4 : Timeline of Discovery of Viroids
10. Page10
Diseases Caused by Viroids - Potato Spindle Tuber Disease
Of themany diseases caused
by Viroids, thespindle tuber
disease of potatoes was the
first to be recognized and
studied by plant pathologists.
Nearly 50 years were to
elapse between initialdescription of this disease in theearly 1920's and theidentificationof
its causalagent, a small, highly-structured, covalentlyclosed circularRNA moleculeknown
as Potato spindletuber viroid (PSTVd). PSTVd remains an important pathogen of potatoand
tomato, and a recent increasein thenumber of reported latent infections of ornamental
species is creating newchallenges for currentdisease management strategies. PSTVdis also a
favoriteobject of study for viroid molecular biologists, thanks in largepart to its ability to
replicateto high titers in tomato where certain strains rapidly inducetheappearanceof a
characteristic diseasesyndromethat includes stuntingand epinasty.
Symptoms and Signs
The naturalhost rangeof PSTVd includes many solanaceous species. Theviroid may cause
disease in Solanumtuberosum (potato), S. lycopersicum (syn. Lycopersiconesculentum,
tomato), and Capsicumannuum (pepper) wheresymptoms may
vary considerably depending on plant species, variety, viroid
strain and environmentalconditions. Infections in other hosts
are symptomless; e.g., Brugmansia spp., Datura sp., Lycianthes
rantonneti (syn. S. rantonneti),Persea
americana (avocado), Physalis peruviana (Capegooseberry), S.
jasminoides, S. muricatum(pepino), and Streptosolen jamesonii.
DISEASE Potatospindle tuber
PATHOGEN Potatospindle tuber viroid
HOSTS potato, tomato, ornamentals (Solanaceae)
Figure 5:- Potato Spindle
Tuber Disease
11. Page11
In potato, growth of infected plants may be severely reduced or even cease entirely; however,
reduction in growth may also be hardly visible. The vines of infected plants may be smaller,
more upright, and producesmaller leaves than their healthy counterparts. Infected tubers
may be small, elongated (from which thedisease derives its name), misshapen, and cracked.
Their eyes may be more pronounced thannormaland may be borneon knob-like
protuberances thatmay even develop intosmall tubers.
The first symptoms of PSTVd infection in tomato(Figure2) are growth reduction and chlorosis
in thetop of the plant. Subsequently, this growth reduction may develop into stunting, and the
chlorosis may become more severe, turningintoreddeningand/or purpling. In this stage,
leaves may becomebrittle. Generally, this stunting is permanent; occasionally,however, plants
may either die or partially recover. As stuntingbegins, flower and fruit initiation stop.
Disease Transmission
PSTVd can be transmitted in four different ways:
Vegetative propagation- Propagationby tubers, cuttings, and
micro-plants provides a very efficient means of viroid
transmission. Onceestablished, PSTVd infection is persistent;
therefore, plants frominfected lots act as a permanent sourceof inoculumfor other lots
and crops. Vegetativepropagation has been themajor pathway for PSTVd transmission
in potatoand ornamentals suchas Brugmansia spp. and S. jasminoides. The absenceof
symptoms increases therisk that infected plants will be used for
propagation
Mechanical transmission- Under favorableconditions, PSTVd
is readily transmittedby normalcultivation activities.This is most
clearly seen with potatoes and tomatoes, whereviroid spread is
mainly along therow
Infected seed and pollen- PSTVdis assumed to havespread
among potato germplasmcollections allover theworld via
infected trueseed. Oncepresent in a germbank, theviroid can be
transmitted toother (wild) potatoplants either mechanically or
12. Page12
by pollen exchange. Seed is also a potentialsourceof infection for other crops such as
tomatoand pepper that arepropagated by seed
Aphid transmission- This routeof transmission requires thesourceplant tobe infected
by both Potatoleafroll virus (PLRV) and PSTVd, thereby limiting thenumber of potential
infection sources. PSTVd is assumed to be encapsidated by the viralcoat protein; such
encapsidation protects theviroid from digestion by micrococcalnucleasein vitro,
suggestingthata similar protectiveeffect may occur in vivo.
Disease Management
Disease management can bedivided intotwo parts: prevention of infection and viroid
eradication.
Prevention of infection includes allmeasures to prevent the introduction of PSTVd intoa
specific crop. It is very important to start a new cultivation with viroid-freeplantingmaterial
(tubers, seeds or plants). PSTVd is considered a quarantine'organism' in many countries, and
therefore, governmentalmeasures toprevent introduction of PSTVd with plants from other
countries will often be applied. Certification schemes includingtestingmay be required to
provide further guarantees thattheplanting materialis free from PSTVd.
In addition tothe use of healthy planting material, it is also important toprevent viroid
introduction via human activities. BecausePSTVd is mechanically transmissible, it can be
introduced intopotentialhost plants via the hands, clothes, or equipment used by people
working in or visiting thegreenhouse. Theuseof disposablegloves and specific clothing and
equipment that stays insidea greenhousecompartmentmay prevent PSTVd introductioninto
greenhouse-growncrops. Furthermore, increasingthenumber of plants species grown in a
greenhousecompartment increases therisk of introduction of PSTVd. Growers should either
growa singlecrop or they should separatedifferent crops and lots, preferably in different
compartments. BecausePSTVd can betransmitted by aphids, plantingPLRV-freeseed potatoes
and controlling aphid populations alsocontributes tothemanagement of PSTVd in potato
crops.
13. Page13
Viroid eradication is based on destruction of PSTVd-infected plantsand thorough cleaningof
equipment and greenhouses whereinfected plants havebeen grown. All infected plants
together with thosefrom an adequate buffer zoneshould be destroyed. In caseof field-grown
potatoes, crop rotations involving non-PSTVd host species help eliminateinfected volunteer
plants. In case of symptomless infections such as thosecommonly observed in ornamentals, all
plants in the lot should be destroyed. Any rock wool or plastic used to cover the soil should
also be removed from thegreenhouseand destroyed. Ideally, all materialslated for disposal
should be transported in a closed container toan incinerator; alternatively, such materialcan
be taken to a refuse dump and covered with a layer of soil.
When PSTVd is identified in a greenhouse-growncrop, allparts of thegreenhouseshould be
thoroughly cleaned, preferably usinga steam cleaner and a scrub brushfor parts that are
difficult toclean (Figure7). A regular acid treatmentcan beused for watering tubes and
drippers. After cleaning thegreenhouseand associated equipment,application of a
disinfectantcompletes theeradication procedure. When cultivationof crops susceptibleto
PSTVd infection resumes, extra monitoringfor PSTVd symptoms and/or testing areadvisable.
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14. Page14
Prions
A prion is an infectious agent, specifically a protein in a misfolded form. The word prion,
coined in 1982 by Stanley B. Prusiner, is derived from thewords protein and infection. The
protein itself, whether in its misfolded or its correctly folded form, can be referred to as the
prion protein (PrP). A protein as an infectious agent stands in contrasttoall other known
infectious agents, likeviruses, bacteria, fungi, or parasites—allof which must contain nucleic
acids (either DNA, RNA, or both). Prions are responsiblefor mammalian transmissible
spongiformencephalopathies, including bovinespongiformencephalopathy(BSE,alsoknown
as "mad cow disease") and scrapiein sheep. In humans, prions cause Creutzfeldt-Jakob
Disease (CJD), variant Creutzfeldt-JakobDisease (vCJD), Gerstmann–Sträussler–Scheinker
syndrome, FatalFamilial Insomnia and kuru. All known prion diseases in mammals affect the
structureof the brain or other neural tissueand all arecurrently untreatableand universally
fatal. In 2013, a study revealed that 1 in 2,000 peoplein theUnited Kingdommight harbour
theinfectious prion protein that causes vCJD.
15. Page15
Diseases Caused by Prions – Bovine Spongiform Encephalopathy
The word BSE is short but it stands for a disease with a long name, bovine spongiform
encephalopathy. "Bovine" means that thedisease affects cows, "spongiform" refers to theway
thebrain from a sick cow looks spongy under a microscope, and "encephalopathy" indicates
that it is a disease of thebrain. BSE is commonly called “mad cow disease.” BSE is a progressive
neurologic diseaseof cows. Progressivemeans that it gets worse over time. Neurologic means
that it damages a cow’s centralnervous system .
Most scientists think thatBSE is caused by a protein called a prion. For reasons that arenot
completely understood, thenormalprion protein changes intoan abnormalprion protein that
is harmful. Thebody of a sick cow does not even knowtheabnormalprion is there. Without
knowing it is there, thecow’s body cannot fight off thedisease.
Symptoms of BSE
A common symptom of BSE is incoordination. Asick cow has troublewalking and getting
up. A sick cow may also act very nervous or violent, which is why BSE is often called “mad
cow disease.”
It usually takes four to six years from the time a cow is infected with theabnormalprion to
when it first shows symptoms of BSE. This is called the incubation period. Duringthe
incubationperiod, thereis no way to tell that a cow has BSE by looking at it. Oncea cow
starts toshow symptoms, it gets sicker and sicker untilit dies, usually within two weeks to six
months. Thereis no treatment for BSE and no vaccinetoprevent it.
Currently, thereis no reliable way to test for BSE in a live cow. After a cow has died, scientists
can tell if it had BSE by looking at its brain under a microscopeand seeing thespongy
appearance. Scientists can alsotell if a cow had BSE by using test kits that can detect the
abnormalprion in thebrain.
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Brain from a healthy cow, as seen under a
microscopeusing specialstains.
Brain from a cow sick with BSE, as seen
under a microscopeusing special
stains. This brain is sponge-like, and the
largewhite spaces are like the "holes" of a
sponge.
Disease Transmission
The parts of a cow that arenot eaten by people are cooked, dried, ground intoa powder, and
used for many purposes, includingas ingredients in animalfeed. A cow gets BSE by eating
feed contaminated with parts that camefromanother cowthat was sick with BSE. The
contaminatedfeed contains theabnormalprion, and a cow becomes infected with the
abnormalprion when it eats the feed. If a cow gets BSE, it most likely ate thecontaminated
feed during its first year of life. Remember, if a cow becomes infected with theabnormal
prion when it is one year old, it usually will not show signs of BSE untilit is five years old or
older.
Table 2:- Comparison of cow brain
brain tissues
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Prevention and control
The measures in the strategy for dealing with BSE are early detection and warning
systems and prevention and rapid responsemeasures and mechanisms in place.
Targeted surveillanceof occurrences of clinicalneurologicaldisease;
Awareness programs to enhancesurveillance;
Screeningtests at routineslaughter;
Transparency in reportingfindingsof BSE;
Safeguardson importation of live ruminantspecies and their products, in
accordancewith theOIE TerrestrialCode;
Removal of specified risk material(SRM) (brain, spinalcolumn) duringslaughter
and processing of carcasses;
Prohibit theinclusion of SRM in animalfeeds, thus removing potentially
contaminatedmaterialfromthe food chain;
Humanedestructionof all suspected and susceptibleanimals exposed to
contaminatedfeed (cohorts);
Appropriatedisposal of carcasses and all animalby-products;
Livestock identificationtoenable effectivesurveillanceand tracing of suspected
livestock.
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BIBILOGRAPHY
i. http://en.wikipedia.org/wiki/Viroid
ii. http://www.ncbi.nlm.nih.gov/pubmed/7121568
iii. http://ghr.nlm.nih.gov/condition/prion-disease
iv. http://en.wikipedia.org/wiki/Prion
v. http://en.wikipedia.org/wiki/Potato_spindle_tuber_viroid
vi. http://www.ncbi.nlm.nih.gov/pubmed/15851027
vii. http://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy
viii. http://www.who.int/zoonoses/diseases/bse/en/
ix. http://www.apsnet.org/edcenter/intropp/lessons/viruses/pages/potatospindletuber.aspx
x. http://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy
xi. http://www.fda.gov/AnimalVeterinary/ResourcesforYou/AnimalHealthLiteracy/ucm136
222.htm
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