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- 1. VIRUS AND BACTERIA SCIED 260 CONCEPTS OF BIOLOGY AND ECOLOGY DEBBIE ANN M. LAGUINDAB MSCIED GENSCI 2
- 2. BACTERIA
- 3. • One of the oldest and most diverse forms of life on Earth. • They lack nucleus and organelles Prokaryotic microorganisms
- 6. ● Flagella – long hair-like filamentous structures that is essential for locomotion of the bacteria. ● Pili - short, hollow, non-helical filamentous structure that aids in adherence to host cells. External structure
- 7. ● Capsule- viscous outermost layer surrounding the cell wall. Aids in adherence and confer resistance against phagocytosis External structure
- 8. ● Cell wall - protects and maintain the shape of the bacteria. GRAM- POSITIVE GRAM - NEGATIVE External structure Gram positive Gram negative peptidoglycan
- 9. Bacteria without a cell wall
- 10. ● Cell membrane – regulates the inflow and outflow of nutrients, ions and metabolites. ● Ribosomes- synthesize bacterial proteins and enzymes ● Nucleiod- DNA molecule either a closed circular or in coiled form Internal structure
- 12. Several bacteria are found in other shapes like; Filamentous (E.g. Actinobacteria, Candidatus savagella, etc. ) Star shaped (E.g. Stella vacuolata, Stella humosa, etc) Comma shaped (E.g. Vibrio spp.) Pleomorphic (E.g. Mycoplasma spp.) Chinese letter like (E.g. Corynebacterium spp.) Lobed (E.g. Sulfolobus spp.) Stalked (E.g. Caulobacter crescentus ) Sheathed (E.g. Leptothrix, Clonothrix)
- 13. ● GRAM STAINING ● OXYGEN REQUIREMENT ● OPTIMUM TEMPERATURE ● ARRANGEMENT OF FLAGELLA ● MODE OF NUTRITION CLASSIFICATION OF BACTERIA
- 14. ● GRAM STAINING CLASSIFICATION OF BACTERIA
- 15. ● OXYGEN REQUIREMENT 1. Aerobic bacteria 2. Facultative bacteria 3. Anaerobic bacteria CLASSIFICATION OF BACTERIA
- 16. ● OPTIMUM TEMPERATURE 1. Psychrophiles 2. Mesophiles 3. Thermophiles CLASSIFICATION OF BACTERIA
- 17. ● ARRANGEMENT OF FLAGELLA CLASSIFICATION OF BACTERIA
- 18. ● MODE OF NUTRITION CLASSIFICATION OF BACTERIA Heterotrophic bacteria Staphylococcus spp
- 19. REPRODUCTION IN BACTERIA ASEXUAL REPRODUCTION • Binary fission • Reproduction through conidia • Budding • Reproduction through cyst formation • Reproduction through endospore formation SEXUAL REPRODUCTION • Transformation • Transduction • Conjugation
- 21. FUNCTIONS AND ROLES OF BACTERIA DECOMPOSITION SYMBIOSIS NITROGEN FIXATION FERMENTATION
- 22. DISADVANTAGES AND LIMITATIONS OF BACTERIA • Wide variety of human diseases • Bacterial spoilage of foods feeds and pharmaceutical products • Can cause disease to crop plants and domestic animals. • Deterioration and degradation of useful organic products like furniture, textiles, etc.
- 25. VIRUS
- 26. Are viruses living or dead?’
- 27. Living Characteristics of Viruses Non-living Characteristics of Viruses Reproduction (ability to replicate) Lack of cellular organization Presence of nucleic acid Lack of metabolic machinery Susceptible to mutation Lack of autonomous reproduction Ability to adapt to changing environment Ability to crystalize Nonresponsive to stimuli Lack of growth
- 28. 1. THE PROGRESSIVE HYPOTHESIS -states that viruses originated from the mobile genetic elements that escaped from the genome of the ancient cellular life or LUCA (last universal common ancestor) and evolved progressively. ORIGIN & EVOLUTION OF VIRUSES
- 29. 2. THE REGRESSIVE HYPOTHESIS It states that viruses were initially small parasitic cells that in time lost all their genetic and cellular components that were not required for the parasitic mode of life and regressively evolved to the current form. . ORIGIN & EVOLUTION OF VIRUSES
- 30. 3. THE VIRUS FIRST HYPOTHESIS -states that viruses existed since the precellular world way before archaea, bacteria, or eukarya. ORIGIN & EVOLUTION OF VIRUSES
- 35. ● Viruses are also being studied as therapeutic agents ● Viruses play an important role in maintaining the ecosystem. ● Viruses are used as vectors in biotechnology ● Viruses can be used as natural pesticides and insecticides. SIGNIFICANCE OF VIRUSES
- 36. VIRAL DISEASES IN HUMAN Human Viral Disease Causative Agent Common cold Rhinovirus, coronavirus, RSV, parainfluenzae virus SARS-CoV, SARS-CoV2, MERS Coronaviruses Rabies Rabies virus (Lyssavirus) Chickenpox, Smallpox Pox viruses Hepatitis Hepatitis viruses Dengue Dengue viruses Chikungunya Chikungunya virus Influenza Influenza viruses Poliomyelitis Poliovirus Encephalitis and Meningitis Japanese encephalitis virus (JEV), Human polyomavirus 2, arbovirus Viral Conjunctivitis Adenovirus, HSV Pneumonia RSV, Influenza virus Types A and B, coronaviruses, adenovirus HIV-AIDS HIV Gastroenteritis Rotavirus, Adenovirus, Noroviruses
- 37. RESEARCH ARTICLE
- 39. Based on Table 3. the level of the most dominant mental model through the drawing writing test is at levels D4 and W2 for the concept of structure and the concept of bacterial reproduction.
- 44. Anoush. (2014, July 20). PPT - BACTERIA PowerPoint Presentation, free download - ID:2016471. SlideServe. https://www.slideserve.com/anoush/bacteria Binary Fission and other Forms of Reproduction in Bacteria. (n.d.). CALS. https://cals.cornell.edu/microbiology/research/active- research-labs/angert-lab/epulopiscium/binary-fission-and-other-forms-reproduction-bacteria Bruslind, L. (2019b, August 1). Introduction to viruses. Pressbooks. https://open.oregonstate.education/generalmicrobiology/chapter/introduction-to-viruses/ Dahal, P. (2023, September 15). What are Bacteria?- A Complete Study Note and Guide. Microbe Notes. https://microbenotes.com/bacteria/ Dahal, P. (2023b, September 30). What are Viruses?- A Complete Study Note and Guide. Microbe Notes. https://microbenotes.com/what-are-viruses/ Hamdiyati, Y., Rahman, T., and Rahmawati, R.D. (2023). Analysis of high school students’ mental model on bacteria concept: representation of students' conceptions. Thabiea : Journal of Natural Science Teaching, 6(1), 76-89. Vedantu. (n.d.). Reproduction in bacteria. VEDANTU. https://www.vedantu.com/biology/reproduction-in-bacteria REFERENCES
- 45. CREDITS: This presentation template was created by Slidesgo, and includes icons by Flaticon and infographics & images by Freepik THANK YOU FOR LISTENING
- 46. 1-5. Draw a bacteria and label its parts. 6-10. Explain why virus is considered the border between living and non living things. QUIZ
Editor's Notes
- The Earth is home to a wide variety of living beings. It is estimated that about 8.7 million species of living beings are currently on the Earth of which 1.2 million species are known to us. These biotic components have total biomass of about 545.8 gigatons, of which 12.8 % is bacterial biomass, while human accounts for only 0.01%. This report provides a overview of bacteria, covering their fundamental characteristics, structure, functions, and their significant roles in both health and the environment. Bacteria, as unicellular microorganisms, play crucial roles in various ecosystems, impacting human health, agriculture, and industry. Understanding the basics of bacteria is essential for appreciating their diverse contributions and potential implications.
- Bacteria are microscopic, unicellular, prokaryotic organisms. They do not have membrane-bound cell organelles and lack a true nucleus, hence are grouped under the domain “Prokaryota” Bacteria, a singular bacterium, is derived from the Ancient Greek word “backērion” meaning “cane”, as the first bacteria observed were bacilli. The study of ‘Bacteria’ is called ‘Bacteriology’; a branch of ‘Microbiology’.
- Bacteria are evolved to adapt and survive in any kind of ecological niches; from normal to extreme environments. Hence, they are ubiquitous. They are found in every possible habitat on the Earth; soil, air, and water. They are associated with all the biotic and abiotic components of the Earth. They are essential components of every ecosystem. Soil is the most heavily habituated place where they constitute about 0.5% W/W of the soil mass. One gram of topsoil may contain as many as one billion bacterial cells. It is estimated that there are approximately 2×1030 bacteria on the Earth, but only around 2% of them are fully studied to date. Hence, there is a huge research gap on the diversity and ecology of many unknown bacterial species.
- Bacteria are unicellular i.e. made up of a single cell. They are prokaryotes and their cells are different from animal and plant cells. In general, the structure of bacteria can be studied as external and internal structures;
- External Structure of a Bacteria It includes a cell wall and all the structures outside the cell wall. 1. Flagella (sing. Flagellum) Flagella are long hair-like filamentous structures. They confer motility to the bacteria. Flagella are divided into three parts; filament, hook, and the basal body. 2. Pili/Fimbriae They are the short, hollow, non-helical filamentous structure that aids in adherence to host cells.
- External Structure of a Bacteria 3. Capsule It is a viscous outermost layer surrounding the cell wall. They are present only in some species of bacteria. . Aids in adherence and confer resistance against phagocytosis
- 4. Cell Wall The cell wall is a rigid structure made up of peptidoglycan that surrounds the plasma membrane as an external coat. It functions as protection and maintains the shape of the bacteria. Based on composition, bacterial cell-wall is classified into 2 types; Gram-positive, and Gram-negative cell walls. The gram-positive cell wall is a thick cell wall containing a large amount of peptidoglycan, about 40 – 90% of the cell wall, arranged in several layer The gram-negative cell wall is a thin cell wall with significantly less amount of peptidoglycan. It is comparatively more complex than the gram-positive cell wall.
- Bacteria without a cell wall Mycoplasma is a minute (50 -300 nm) bacteria without a cell wall. They do not have a fixed shape.
- It includes the cell membrane and all the structures inside the cell membrane. 1. Cell membrane/Plasma membrane It is the innermost phospholipid bilayer, just beneath the cell wall, enclosing cytoplasm. It regulates the inflow and outflow of nutrients, ions, and metabolites Ribosomes - Their main role is to synthesize bacterial proteins and enzymes. They are target sites for different antibiotics like erythromycin, macrolides, aminoglycosides, etc. Nucleiod- Bacterial DNAs are found either in nucleoid as chromosomal DNA or outside nucleoid as a plasmid.
- Basically, bacteria are of four distinct shapes, cocci, bacilli, spiral, and comma-shaped. a. Cocci shape bacteria They are spherical bacteria. Based on the arrangement of cells they are further sub-grouped as; b. Bacilli shape bacteria They are rod-shaped bacteria. Based on the arrangement of cells they are also sub-grouped as; c. Spiral They are long helical-shaped or twisted bacteria. Eg. Spirilla spp. , Spirochetes spp. , etc.
- 1. Gram-Positive Bacteria Bacteria having a thick peptidoglycan layer and retaining the purple color of crystal violet during Gram staining Bacteria having a thin peptidoglycan layer and losing crystal violet but retaining pink / red color of counterstain safranine during Gram staining
- Aerobic bacteria They respire aerobically and can’t survive in anoxic environments. E.g. Pseudomonas aeruginosa, Nocardia spp., Mycobacterium tuberculosis, etc. 2. Facultative aerobes They survive in very low oxygen levels and can survive in both oxygenic and anoxic environments. They are Microaerophiles. E.g. E. coli, Klebsiella pneumoniae, Lactobacillus spp., Staphylococcus spp., etc. 3. Anaerobic bacteria They respire anaerobically and can’t survive in an oxygen-rich environment. E.g. Clostridium perfinges, Campylobacter, Listeria, Bifidobacterium, Bacteroides, etc.
- Bacteria are classified broadly into 3 types as; 1. Psychrophiles They have optimum growth temperature at 150C or below. E.g. Chryseobacterium, Psychrobaceter, Polaromonas, Sphingomonas, Alteromonas, Hyphomonas, Listeria monocytogenes, etc. 2. Mesophiles They have optimum growth temperature at 15 – 450C. Pathogenic bacteria fall in this category. E.g. E. coli, Staphylococcus aureus, Salmonella Typhi, Streptococcus pyogenes, Klebsiella spp., Pseudomonas spp., etc. 3. Thermophiles They have optimum growth temperature at above 450C. E.g. Bacillus thermophilus, Methanothrix, Archaeglobus, Thermophilus aquaticus, Geogemma barosii (at 1220C), Pyrolobus fumarii (at 1130C), Pyrococcus spp., etc.
- Bacteria are classified into 5 types as; 1. Atrichous They are bacteria without flagella. E.g. Lactobacillus spp., Bacillus anthracis, Staphylococcus spp., Streptococcus spp., etc. 2. Monotrichous They are bacteria with only one flagellum at one pole. E.g. Campylobacter spp., Vibrio cholerae, etc. 3. Lophotrichus They are bacteria with multiple flagella at one end. E.g. Spirillum, Helicobacter pylori, Pseudomonas fluorescence, etc. 4. Peritrichous They are bacteria with multiple flagella projecting in all directions. E.g. E. coli, Klebsiella, Proteus, Salmonella Typhi, etc. 5. Amphitrichous They are bacteria with one flagellum at each pole. E.g. Alcaligenes faecalis, Nitrosomonas, etc.
- Classification of Bacteria based on mode of nutrition 1. Autotrophic bacteria They are bacteria capable of assimilating inorganic matters into organic matters i.e. capable of preparing their food like plants. They are of 2 types; Photoautotrophs; They use energy from sunlight for assimilation. It includes cyanobacteria (Nostoc, Prochlorococcus, etc.), purple sulfur bacteria (Nitrosococcus, Thiococcus, Halochromatium, etc.), purple non-sulfur bacteria (Rhodopseudomonas spp.), green sulfur bacteria (Chlorobium, Chromatium, etc.) Chemoautotrophs; They use chemical energy for assimilation. It includes sulfur bacteria (Beggiatoa, Thiobacillus, Thiothrix, Sulfolobus, etc.), nitrogen bacteria (Nitrosomonas, Nitrobacter, etc.), hydrogen oxidizing bacteria (H. pylori, Hydrogenbacter, Hydrogenvibrio marinus, etc.), methanotrophs (Methylomonas, Methylococcus, etc), iron bacteria (Thiobacillus ferroxidans, Ferrobacillus, Geobacter metallireducens, etc.) 2. Heterotrophic bacteria They are bacteria that derive energy by consuming organic compounds, but they do not convert organic compounds to inorganics. They are parasitic or symbiotic types. E.g. E. coli, Rhizobium spp., Staphylococcus spp., Mycobacterium spp., Klebsiella pneumoniae, etc.
- In asexual reproduction in bacteria, there are five following types of Asexual reproduction: Binary fission Reproduction through conidia Budding Reproduction through cyst formation Reproduction through endospore formation SEXUAL REPRODUCTION Transformation Transduction Conjugation
- It is the most common type. Under favorable conditions, each bacterium divides into two identical bacteria. The bacterial cells first acquire nutrition grow at their maximum size and replicate their DNA. The new replicated DNA called an incipient nucleus, migrates towards opposite poles. A transverse septum begins to develop and separate the two daughter cells.
- Functions and Roles of Bacteria: a. Decomposition: Bacteria play a crucial role in breaking down organic matter, recycling nutrients, and contributing to nutrient cycles in ecosystems. b. Symbiosis: Many bacteria form symbiotic relationships with plants, animals, and humans, providing essential benefits for both parties. c. Nitrogen Fixation: Certain bacteria convert atmospheric nitrogen into a form that plants can use, contributing to soil fertility. d. Fermentation: Bacteria are involved in various industrial processes, such as food fermentation and the production of antibiotics.
- Different pathogenic bacteria are responsible for a wide variety of human diseases from simple to life-threatening. Bacterial diseases are responsible for thousands of death each year. Bacterial spoilage of foods feeds and pharmaceutical products is another disadvantage. The food and pharma industries have to bear huge losses due to bacterial spoilage. Several bacteria like denitrifying bacteria, sulfur-oxidizing bacteria, etc. are responsible for decreasing the fertility of the soil, ultimately reducing crop yields. Bacteria can cause disease to crop plants and domestic animals. This will reduce agricultural production. Bacteria cause deterioration and degradation of useful organic products like furniture, textiles, etc.
- C. Some bacteria are pathogens, meaning they cause disease 1. Disease is caused by 2 means: damaging the tissue they are eating or releasing toxins
- Bacteria are incredibly diverse microorganisms with significant implications for various aspects of life on Earth. Understanding their structure, functions, and roles is crucial for harnessing their beneficial aspects and mitigating potential negative impacts, especially in the context of human health and environmental sustainability. Ongoing research continues to unveil the mysteries of bacterial life, paving the way for innovative applications and discoveries.
- Viruses are obligatory parasitic infectious biological particles possessing only one type of nucleic acid and requiring the host cell’s mechanism to replicate. The word ‘virus’ is derived from the Latin word ‘vīrus’ which means poisonous fluid or venom. The study of viruses is called virology and it is one branch of microbiology. However, viruses are not considered microorganisms. In fact, they are not even considered living things. ‘
- Viruses exhibit characteristics of both living and non-living things; hence, it is unclear to claim either they are living or non-living. Instead, they are considered a border between living and non-living and often defined as acellular particle.
- However, this hypothesis fails to explain the unique structures (capsid and others) present in the viruses but not in other cells.
- The prominence of genes in viruses without cellular counterparts is one major critique of this hypothesis. Additionally, besides viruses, no other, even the smallest parasites, resemble viruses in any way.
- During the period when inorganic molecules were aggregating and reacting to form organic molecules and thus formed organic molecules were aggregating to form a living entity, viruses may have been created from the aggregation of proteins and nucleic acids. Over time, enzymes for synthesizing membranes, cell walls, and other cellular components evolved forming a true cell, but viruses remained in their acellular form and gained the capacity to infect cellular life and replicate
- Viruses are simple in design. An extracellular, complete, infectious stage of a virus is called a virion. In general, a virion consists of a viral genome (RNA or DNA) surrounded by a protein coat called capsid. Some virions may contain envelope derived from the host’s plasma membrane. 1. Nucleic Acid (Viral Genome) A virion contains only one type of nucleic acid, either DNA or RNA, as its genome but never both. Viruses containing RNA as their genome are called RNA viruses and viruses containing DNA as their genome are called DNA viruses 2. Capsid The viral genomes are externally coated by a shell of proteins called capsid. Capsid is a polymeric structure made of structural subunits called capsomers which in turn are made of different kinds of proteins. Capsid protects the viral genome from any physical or chemical stresses, contains attachment sites to adhere to the host cell, and helps to penetrate the host cell. 3. Envelope Some viruses are externally covered by a lipid bilayer membrane called an envelope. Viral envelopes are derived from the host’s plasma membrane; hence, they are composed of lipid bilayers as in the plasma membrane
- Viruses display a wide diversity in their shape and size. Some may be as small as 20 nm in diameter while some may reach up to 1400 nm in length and 80 nm in diameter. Giant viruses measuring up to 400 nm in diameter have also been discovered. The viral capsid generally has two basic symmetry or structures viz. helical or icosahedral structure. Hence, most viruses are morphologically either helical or icosahedral, although, a few have complex structures. Examples of icosahedral viruses include hepatitis B virus, dengue virus, parvovirus, rhinovirus, human papillomavirus, herpes virus, etc. It is a spiral shape in which capsid curves cylindrically around a central axis (nucleic acid core). These shape of viruses are energy efficient as they require less free energy to assemble capsid than required by icosahedral or complex viruses. Examples of helical viruses include Tobacco mosaic virus, influenza virus, measles virus, mumps virus, rabies virus, Ebola virus, etc. A few viruses show unique architectures that are neither helical nor icosahedral. Such structures are called complex structures. Bacteriophages, poxviruses, geminiviruses, etc. show complex structures.
- Many bacteriophages have icosahedral heads connected to cylindrical tail sheaths.
- While the replication cycle of viruses can vary from virus to virus, there is a general pattern that can be described, consisting of five steps: Attachment. Outside of their host cell, viruses are inert or metabolically inactive. Therefore, the encounter of a virion to an appropriate host cell is a random event. The attachment itself is highly specific, between molecules on the outside of the virus and receptors on the host cell surface. This accounts for the specificity of viruses to only infect particular cell types or particular hosts. Penetration or Viral Entry. Many unenveloped (or naked) viruses inject their nucleic acid into the host cell, leaving an empty capsid on the outside. This process is termed penetration and is common with bacteriophage, the viruses that infect bacteria. With the eukaryotic viruses, it is more likely for the entire capsid to gain entrance into the cell, with the capsid being removed in the cytoplasm. An unenveloped eukaryotic virus often gains entry via endocytosis, where the host cell is compelled to engulf the capsid resulting in an endocytic vesicle, allowing the virus access to the cell contents. An enveloped eukaryotic virus gains entrance for its nucleocapsid through membrane fusion, where the viral envelope fuses with the host cell membrane, pushing the nucleocapsid past the cell membrane. If the entire nucleocapsid is brought into the cell then there is an uncoating process to strip away the capsid and release the viral genome. Synthesis The synthesis stage is largely dictated by the type of viral genome, since genomes that differ from the cell’s dsDNA genome can involve intricate viral strategies for genome replication and protein synthesis. Viral specific enzymes, such as RNA-dependent RNA polymerases, might be necessary for the replication process to proceed. Protein production is tightly controlled, to insure that components are made at the right time in viral development. Assembly The complexity of viral assembly depends upon the virus being made. The simplest virus has a capsid composed of 3 different types of proteins, which self-assembles with little difficulty. The most complex virus is composed of over 60 different proteins, which must all come together in a specific order. These viruses often employ multiple assembly lines to create the different viral structures and then utilize scaffolding proteins to put all the viral components together in an organized fashion. Release The majority of viruses lyse their host cell at the end of replication, allowing all the newly formed virions to be released to the environment. Another possibility, common for enveloped viruses, is budding, where one virus is released from the cell at a time. The cell membrane is modified by the insertion of viral proteins, with the nucleocapsid pushing out through this modified portion of the membrane, allowing it to acquire an envelope.
- ALTHOUGH Viruses are the major causes of disease in all life forms including humans. Viruses are also being studied as therapeutic agents to treat cancer and genetic disorders and to kill pathogenic microorganisms (like phage therapy). Viruses play an important role in maintaining the ecosystem. In aquatic environments, viruses are the most abundant entities and they help to regulate biogeochemical cycles and maintain aquatic microbiome and aquatic ecosystem. Viruses are used as vectors in biotechnology to deliver genes coding desirable characteristics to the genome of the recipient cell. Viruses can be used as natural pesticides and insecticides.
- Humans are susceptible to different pathogenic viruses and time and again humanity has suffered from different viral epidemics