Genetic of microorganisms provides advantages for genetic research due to their simple genome structures, universal gene code, lack of diploid chromosomes and dominant genes, ease of cultivation, rapid reproduction, genetic population heterogeneity, and accessibility of modern genetic analysis methods. Bacteria like E. coli have smaller, supercoiled DNA compared to human cells. Bacterial genomes contain structural and regulatory genes organized into operons that control gene expression. The lac and arg operons demonstrate inducible and repressible gene regulation through repressor proteins and substrate/product binding. Mutation, recombination, and mobile genetic elements allow for genetic variation and horizontal gene transfer between microorganisms.
Mechanism of pathogenicity-Exotoxin and endotoxinaiswarya thomas
Brief description on mechanisms of pathogenicity, actions of toxins produced by various bacteria and notable endotoxins and exotoxins. Mechanism of action of some of the commonest endotoxins and exotoxins are explained.
Microbial Taxonomy - Dr. R Subashkumar, Associate Professor in Biotechnology, Sri Ramakrishna College of Arts and Science (Autonomous), Coimbatore-641006
Immunity are divided into nonspecific immunity and specific immunity. Examples of nonspecific immunity are skin, mucous membrane, and sebum. Specific immunity recognizes and respond to specific foreign substance. Specific immunity are divided into humoral response and cell-mediated response. Humoral response involves the production of antibodies while cell mediated immunity involve the cytotoxic T cells.
Mechanism of pathogenicity-Exotoxin and endotoxinaiswarya thomas
Brief description on mechanisms of pathogenicity, actions of toxins produced by various bacteria and notable endotoxins and exotoxins. Mechanism of action of some of the commonest endotoxins and exotoxins are explained.
Microbial Taxonomy - Dr. R Subashkumar, Associate Professor in Biotechnology, Sri Ramakrishna College of Arts and Science (Autonomous), Coimbatore-641006
Immunity are divided into nonspecific immunity and specific immunity. Examples of nonspecific immunity are skin, mucous membrane, and sebum. Specific immunity recognizes and respond to specific foreign substance. Specific immunity are divided into humoral response and cell-mediated response. Humoral response involves the production of antibodies while cell mediated immunity involve the cytotoxic T cells.
Unit 6: Diversity of Microbial Mats
LECTURE LEARNING GOALS
1. Definemicrobialmats.Describethe functional guilds of microbes in the different layers, and how they interact.
2. Foreachofthethreephylaof photosynthetic bacteria, contrast how each fixes C and gains energy and reducing equivalents from light.
3. Forthetwothermophilicbacterialphyla, describe their adaptations to life at high
temperature. Explain how they are primitive and deeply-branching.
Difference between innate and adaptive immunitykamilKhan63
Adaptive Immunity : it is the immune response against a specific antigen.
Innate Immunity : it is the immediate protective response of the immune system that does not require previous exposure to the antigen.
Immunology - Innate and Acquired ImmunityShigina E S
Title: Innate and Acquired Immunity: Understanding the Two Branches of Our Immune System
Introduction:
The human immune system is a complex network of cells, tissues, and organs that protects us from invading pathogens and foreign substances. In this presentation, we will explore the two branches of the immune system: innate and acquired immunity. We will discuss the key features of each branch, their mechanisms of action, and how they work together to keep us healthy.
Section 1: Innate Immunity
- Innate immunity is the first line of defense against pathogens and foreign substances.
- We will discuss the key features of innate immunity, including physical barriers, such as skin and mucous membranes, and the cellular and molecular components of innate immunity, such as phagocytes and cytokines.
- We will also explore some of the ways in which innate immunity can be activated and how it responds to different types of pathogens.
Section 2: Acquired Immunity
- Acquired immunity, also known as adaptive immunity, is a more specialized and targeted response to specific pathogens or foreign substances.
- We will discuss the key features of acquired immunity, including the role of B and T lymphocytes, antibodies, and memory cells.
- We will also explore some of the ways in which acquired immunity can be activated, including through vaccination, and how it responds to specific antigens.
Section 3: Interaction between Innate and Acquired Immunity
- Innate and acquired immunity work together in a coordinated manner to provide effective protection against pathogens and foreign substances.
- We will discuss how innate immunity can initiate an immune response and activate acquired immunity, and how acquired immunity can enhance the effectiveness of innate immunity.
- We will also explore some examples of how these two branches of the immune system work together in different types of infections.
Conclusion:
Understanding the different branches of our immune system is essential for developing effective strategies to prevent and treat infectious diseases. Innate and acquired immunity work together to provide a coordinated and dynamic defense against pathogens and foreign substances. By exploring the mechanisms and interactions between these two branches of the immune system, we can gain a deeper appreciation for the complexity and power of our immune system.
Unit 6: Diversity of Microbial Mats
LECTURE LEARNING GOALS
1. Definemicrobialmats.Describethe functional guilds of microbes in the different layers, and how they interact.
2. Foreachofthethreephylaof photosynthetic bacteria, contrast how each fixes C and gains energy and reducing equivalents from light.
3. Forthetwothermophilicbacterialphyla, describe their adaptations to life at high
temperature. Explain how they are primitive and deeply-branching.
Difference between innate and adaptive immunitykamilKhan63
Adaptive Immunity : it is the immune response against a specific antigen.
Innate Immunity : it is the immediate protective response of the immune system that does not require previous exposure to the antigen.
Immunology - Innate and Acquired ImmunityShigina E S
Title: Innate and Acquired Immunity: Understanding the Two Branches of Our Immune System
Introduction:
The human immune system is a complex network of cells, tissues, and organs that protects us from invading pathogens and foreign substances. In this presentation, we will explore the two branches of the immune system: innate and acquired immunity. We will discuss the key features of each branch, their mechanisms of action, and how they work together to keep us healthy.
Section 1: Innate Immunity
- Innate immunity is the first line of defense against pathogens and foreign substances.
- We will discuss the key features of innate immunity, including physical barriers, such as skin and mucous membranes, and the cellular and molecular components of innate immunity, such as phagocytes and cytokines.
- We will also explore some of the ways in which innate immunity can be activated and how it responds to different types of pathogens.
Section 2: Acquired Immunity
- Acquired immunity, also known as adaptive immunity, is a more specialized and targeted response to specific pathogens or foreign substances.
- We will discuss the key features of acquired immunity, including the role of B and T lymphocytes, antibodies, and memory cells.
- We will also explore some of the ways in which acquired immunity can be activated, including through vaccination, and how it responds to specific antigens.
Section 3: Interaction between Innate and Acquired Immunity
- Innate and acquired immunity work together in a coordinated manner to provide effective protection against pathogens and foreign substances.
- We will discuss how innate immunity can initiate an immune response and activate acquired immunity, and how acquired immunity can enhance the effectiveness of innate immunity.
- We will also explore some examples of how these two branches of the immune system work together in different types of infections.
Conclusion:
Understanding the different branches of our immune system is essential for developing effective strategies to prevent and treat infectious diseases. Innate and acquired immunity work together to provide a coordinated and dynamic defense against pathogens and foreign substances. By exploring the mechanisms and interactions between these two branches of the immune system, we can gain a deeper appreciation for the complexity and power of our immune system.
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
A short yet comprehensive presentation on bacterial genetics, an important microbiology topic for BDS 2nd, MBBS 2nd and MD/MS /MDS 1st . Made using CP Baveja's Textbook of Microbiology. Meant as an introduction and overview with stress on some key areas.
Topics covered: Basic Principles, Synthesis of Protein, Extra Chromosomal Genetic Material, Bacterial Variation , Gene Transfer, Genetic Mechanisms of Drug Resistance, Genetic Engineering, DNA Probes, Polymerase Chain Reaction, Genetically Modified Organisms and Gene Therapy.
Structure of DNA. Coiling of DNA. Definitions about genetics. The Gene & The Genetic Code. Gene Mutation. Regulation of gene expression. DNA Functions. Patterns Of Inheritance
A brief Power Point Presentation providing an overview about Genetic improvements through Biotechnology in Cereal Crops with precise and well known procedures and examples helping students about their academics on professional level in related fields.
Content for this compilation (Power Point Presentation) was collected from Different sources: Internet, books, social media, research papers, websites etc. and I definitely admire and acknowledge all these sources to provide such a helpful content.
This Presentation was prepared and presented during Bachelors degree in Agriculture (Session 2014-2018) with major subject of Plant Breeding and Genetics at "University College of Agriculture and Environmental Sciences, Baghdad-ul-Jadeed Campus, The Islamia University of Bahawalpur, Pakistan" as an Assignment on the topic of "Genetic Improvement Through Biotechnology in Cereal Crops".
I hope, content might be helpful on academic and professional level.
Best Regards
Muhammad Raza Ullah Tariq
Similar to Bohomolets Microbiology Lecture #6 (20)
HIV discrimination among health providers in Malaysia by Dr RubzDr. Rubz
Although doctors took oath that they will treat everyone the best they can and without judging anyone but discrimination still exist especially in HIV affected people. Due to this issue, Pertubuhan Advokasi Masyarakat Terpinggir Malaysia has taken a step to engage with doctors at government sector and desensitize them and find the line to stand together.
Testicular cancer for public awareness by Dr RubzDr. Rubz
A presentation prepared for Charity Dinner with Fun Charity. All the profits of the event will go to FReHA (a NGO which supports women's and reproductive health.)
Prostate cancer for public awareness by DR RUBZDr. Rubz
A presentation prepared for Charity Dinner with Fun Charity. All the profits of the event will go to FReHA (a NGO which supports women's and reproductive health.)
Breast Cancer for public awareness by Dr RubzDr. Rubz
A presentation prepared for Charity Dinner with Fun Charity. All the profits of the event will go to FReHA (a NGO which supports women's and reproductive health.)
This is the first phase (qualitative) of the current project we are working on with the supervision of University Malaya and Yale School of Medicine.It will be publish as IBBS 2013 by end of the year. This slide is just a rough picture of what we are doing at the moment. This is copyright protected!
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
Atrioventricular conduction blocks ( AV blocks ) are classified into 3 types.
This document describes the acute management of AV block.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
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TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
3. Competitive structure genome of E.coli and human cell Hours Minutes Time existence of mRNA Histones Polyamines DNA combined in cell with Absent Present Plasmid Diploid Haploid Genome type Absent Present Introns Linear Supercoiled DNA shape 183 см 0,1 см DNA length 2х10 12 2х10 9 Molecular weight of DNA 100000 4000 Quantity of genes 46 1 Quantity of chromosomes Nucleus Nucleoid Place in cell Human cell E.coli Properties
4. The genome is the some total of genetic material of a cell
17. Selected mutagenic agents and their effects Cause frameshifts due to insertion between base pairs Acridine dyes Compete with natural bases for sites on replicating DNA Notrogen base analogs Radiation Causes cross-links between adjacent pyrimidines Ultraviolet Form free radicals that cause single or double breaks in DNA Ionizing (gamma rays) Causes cross-linkage of DNA strands Mustard gas Removes an amino group from some bases Nitrous acid, disulfite Chemical Effect Agent
18.
19. Competitive characteristic IS, transposons, and plasmids 40-50 different genes Only few genes for transposase and resistance to antibiotics Only genes for transposase Quantity of genes No 800-1400 pair nucleic bases IS Yes 3000-5000 pair nucleic bases Plasmid No 2000-2500 pair nucleic bases Transposon Self-dependent replication DNA size Genetic element
21. Plasmid Chromosomal and plasmid DNA leaking out of a cell.
22. Cell functions coded for by some plasmids Utilization of camphor Formation of spores in streptomycetes Metabolic plasmids Enterotoxin production Fimbriae production Virulence factor plasmids Bacteriocin production Col plasmids Resistance to various antibiotics Resistance to cadmium and mercury Resistance to ultraviolet radiation Resistance plasmids (R) Transfer of DNA from one cell to another via conjugation (F-pili) Fertility plasmids (F) Function Group
24. Types of intermicrobial exchange Toxins; enzymes for fermentation; drug resistance Indirect Donor is lysed bacterium Defective bacteriophage is carrier of donor DNA Live, competent recipient cell of came species as donor Transduc-tion Polysaccharide capsule Indirect Free donor DNA (fragment) Live, competent recipient cell Transfor-mation Drug resistance, resistance to metal; enzymes; degradation of toxic substrate Direct Sex pilus on donor Fertility plasmid in donor Both donor and recipient Gram-negative cells Conjuga-tion Genes transferred Direct of indirect Requirement Mode
25. Conjugation Conjugation is mode of sexual process mating in which a plasmid or other genetic material is transferred by a donor to a recipient cell via a specialized appendage
26. Conjugation process Sex, or F, pilus holding together donor and recipient cell of E.coli during DNA transfer
27. Participants of conjugation process Gram-negative bacterium that produce F pili act as donors during conjugation. Donor strains are designated F + if the F plasmid is independent Bacteria lacking the F plasmid are recipients and designated F - If the F plasmid DNA incorporated into the bacterial chromosome the donor cell designated Hfr ( high frequency recombination )
29. Transformation F + to Hfr cell The F plasmid integrates at specific locations into the chromosome and F + cell is transformed to Hfr cell. The process is reversible.
38. Specialized transduction In specialized transduction, a highly specific part of the host genome is regularly incorporated into the virus. It occurs only during infection caused by temperate phage a) b) c) d) e) f)
Editor's Notes
The genome of procaryotes is quite small compared with the genomes of eucaryotes. Bacterial DNA consists of a few thousand genes in one circular chromosome. Eucaryotic genomes range from thousands to hundreds of thousands of genes. Their DNA is packaged in tightly wound spirals arranged in discrete chromosome.
DNA copies itself just before cellular division by the process of semiconservative replication. Semiconservative replication means that each “old” DNA strand is the template upon which each “new” strand is synthesized. The circular bacterial chromosome is replicated at two forks as directed by DNA polymerase III. At each fork, 2 new strands and synthesized – 1 continuously and 1 in short fragments, so called “Okazaki fragments”.
There are hypotheses that introns serve as a stock for extra bits of genetic material that could be available for splicing into existing genes, thus promoting genetic change and evolution. With losing of introns procaryotes have lost and grate potential to evolution, that have eucaryotes, but bacteria have acquired very rapid metabolism and reproduction. Eucaryotic cells and viruses have introns
Operon contain various control genes (regulators, promoters, and operators) that govern the operation of related structural genes. Such gene regulation responds to external stimuli and usually occurs at the level of transcription.
The lac operon controls the utilization of lactose. Tree structural genes under the control of the lac promoter (Plac) code for the synthesis of the enzymes needed for lactose utilization. These enzymes are made only when lactose is present.
In inductive systems like the lac operon , the operon is normally in an off mode and does not initiate enzyme synthesis when the appropriate substrate is absent. Structural gene–regular codes special protein – repressor. In the absence of lactose, this repressor binds with the operator lacus, thereby blocking the transcription of the structural genes lying downstream (a). If lactose is added to the cell’s environment, it triggers several events that turn the operon on . The binding of lactose to the repressor protein causes a conformational changes in the repressor that dislodges it from the operator segment (b). The control segment that was previously inactive is now unlocked, and RNA polymerase can now bind to the promoter. The structural genes are transcribed in a transcript coding for all 3 enzymes. After that 3 separate proteins for degradation of lactose are synthesized and digest lactose.. Lactose vanish from environment, repressor becomes free and lock operator.
Bacterial systems for synthesis of amino acids, purines, and pyrimidines work on a different principles – that of repression. Similar factors such as repressor proteins, operators, and a series of structural genes exist for this operon, but with some important differences. Unlike the lac operon, this operon is normally in the on mode and will be turned off only when this nutrient is no longer required. The nutrient plays an additional role as a corepressor needed to block the action of the operon. In cell all synthesized arginine are immediately used in metabolism. Under this conditions, the arg operon is set to on , and arginine is being actively synthesized. If cell has surplus of arginine, it accumulate. The free arginine as then available to act as a corepressor by attaching to the repressor. Arginine activates inactive repressor. Repressor locks operator and stops transcription and arginine synthesis.
Because adding or deleting a single base pair changes the reading frame of the transcribed mRNA. The deletion or addition of a single or double (but not 3) base pair can have as great an effect as a large deficiency.
Because the genetic code is degenerate, the substitution of one nucleotide base for another nay not change the amino acid specified by the codon. Because same amino acid may be coded by triplets with different base, for instance, ACU, ACC, ACG and ACA all code for threonine, so a mutation that changes only last base will not alter the sense of the message in any way. Changes in a single amino acid within a polypeptide often do not drastically reduce the activity of an enzyme and are rarely fatal to the microorganism.
An insertion sequence can move around bacterial chromosomes so that at different times it is found at different locations on the chromosome. The nucleotide bases in the IS regions often do not appear to code for structural proteins but may have a regulatory function. They code for transposase, an enzyme that is required for transposition. Transposons are transposable genetic elements that contain genetic information for the production if structural proteins, usually for antibiotic resistance. IS elements and transposons can not be situated free in cytoplasm, but only in integrative form in chromosome or plasmid. They can not self-dependent replicate as plasmid. Transposable elements as IS and transposon can move from sites on the chromosome of cells into plasmid, which are rapidly transferred by conjugation to other cells.
An insertion sequence can move around bacterial chromosomes so that at different times it is found at different locations on the chromosome. The nucleotide bases in the IS regions often do not appear to code for structural proteins but may have a regulatory function. They code for transposase, an enzyme that is required for transposition. Transposons are transposable genetic elements that contain genetic information for the production if structural proteins, usually for antibiotic resistance. Transposable elements as IS and transposon can move from sites on the chromosome of cells into plasmid, which are rapidly transferred by conjugation to other cells.
Note the relative sizes of the 2 kinds of DNA.
Colicin is protein similar to antibiotic but it toxic only to closely related bacteria. Activity of colicinigenic plasmids acts to eliminate competitors.
Four natural process lead to movement of DNA from a donor to a recipient cell. Plasmid transfer, transformation (transfer of naked DNA), transduction (transfer of DNA via a phage), and conjugation (transfer by direct mating contact) can lead to recombination of DNA.
Depending upon the mode of transmission, the means of genetic recombination is called C., T., Tr.
The physical contact between mating cells is established by the F pilus.
Some bacterial cells contain F plasmids that contain the genes that code for the F pilus and the transfer of DNA from a donor cell to a recipient.
The F plasmid in the donor cell carries the genetic information for the synthesis of the sex pilus, the organelle that attaches the donor to the recipient cell. If the donor cell F+ loses the F plasmid, it becomes F – because it can no longer synthesize the sex pilus and attacn to the recipient cell. Within minutes after contact, the F plasmid from the donor cell enters the recipient cell. Because F – cell receive the F plasmid, it quickly becomes F+. Cell donor do not loss F plasmid, because only one strand is transferred to donor cell. And the complementary strand is synthesized in both cells. In addition, any other plasmids the donor cell contains, such R plasmid, may also be transferred, but not cell chromosome.
In the Hfr cell, the F plasmid replicates as part of the chromosome. Thus, the progeny of an Hfr cell are also Hfr.
The F plasmid must be incorporated into the chromosome for the donor chromosome to be transferred into the recipient cell. When the Hfr and F – cells contact each other, the circular donor chromosome breaks at the site at which the F plasmid is integrated. The part of chromosome is transported into the recipient cell and integrate into the recipient chromosome. Donor cell synthesizes complementary strand.
DNA from lysed dead cell get into solution and recipient bacterium takes up the DNA. To take up DNA, a recipient call must be competent, that is, it must have a site for binding the donor DNA at the cell surface and its plasma membrane must be in a state so that free DNA can pass across it. When dead cells which can form capsule are mixed with live noncapsuled bacteria, transformation occurs, and DNA containing genes for capsule production is taken up by the living bacteria that normally lack the genetic information for capsule production.
Griffith experiment. The Streptococcus pneumoniae exists in 2 major strains based on the presence of the capsule. Encapsulated strains bears a smooth S colonies and are virulent, strains lacking a capsule have a rough R colonies and are nonvirulent. When a mouse was infected with a live, virulent strain, it soon died.
When another mouse was infected with a live nonvirulent strain, the mouse remained alive and healthy.
Next, Griffith heat-killed an virulent S strain and injected it into a mouse, which remained healthy.
Then Griffith injected both dead S virulent encapsulated streptococci and live R cells without capsule into a mouse. At result, mouse have dead from pneumococcal infection. And live encapsulated virulent Streptococcus pneumoniae was isolated from the mouse. Recombination occurs and the progeny of the transformed bacteria become capable of producing capsules and were transformed into virulent.
In generalized transduction, random fragments of disintegrating host DNA are taken up by the phage during assembly. Virtually any gene from the bacterium can be transmitted through this means. After that, phage with fragment of donor DNA infect other bacterium, and the DNA incorporate into its chromosome.
The DNA of a temperate phage enters into the bacterial host cell The phage DNA may become integrated with host cell DNA as a prophage When the prophage is induced to leave the bacterial chromosome, it may carry along a piece of bacterial DNA in place of phage DNA. The phage that are replicated are defective because they lack viral genes that have been replaced by bacterial DNA The defective phage DNA enters new host cell but cannot cause the production of new phage particles Bacterial genes introduced into the new host cell are integrated into the DNA, become a part of the bacterial chromosome, and are replicated along with the rest of the bacterial DNA. Several cases of specialized transduction have medical importance. The virulent strains of Corinebacterium diphtheriae produce toxin, whereas nonvirulent strains do not produce toxin. It turn out that virulence is due entirely to lysogenic conversion, in which a bacteriophage introduces genes that code for toxin. Only those bacteria infected with a temperate phage are toxin formed.