Bacteriophages

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Bacteriophages

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Bacteriophages :

Bacteriophages Dr.T.V.Rao MD 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 1

What are Bacteriophages:

What are Bacteriophages Viruses that attack bacteria were observed by Twort and d'Herelle in 1915 and 1917. They observed that broth cultures of certain intestinal bacteria could be dissolved by addition of a bacteria-free filtrate obtained from sewage 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 2

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Bacteriophages under Electron Microscope:

Bacteriophages under Electron Microscope 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 4

Bacteriophage (Phage):

Bacteriophage (Phage) Definition - Obligate intracellular parasites that multiply inside bacteria by making use of some or all of the host biosynthetic machinery Significance Models for animal cell viruses Gene transfer in bacteria Medical applications Identification of bacteria - phage typing Treatment and prophylaxsis??? 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 5

Bacteriophages: Definition & History:

Bacteriophages: Definition & History Bacteriophages are viruses that can infect and destroy bacteria. They have been referred to as bacterial parasites, with each phage type depending on a single strain of bacteria to act as host. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 6

BACTRIOPHAGES:

BACTRIOPHAGES Like most viruses, bacteriophages typically carry only the genetic information needed for replication of their nucleic acid and synthesis of their protein coats.. They require precursors, energy generation and ribosomes supplied by their bacterial host cell. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 7

Bacteriophages: Classification :

Bacteriophages: Classification At present, over 5000 bacteriophages have been studied by electron microscopy and can be divided into 13 virus families. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 8

Bacteriophage:

Bacteriophage Bacteriophages make up a diverse group of viruses, some of which have complex structures, including double-stranded DNA. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 9

Bacteriophage:

Bacteriophage 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 10

Bacteriophage:

Bacteriophage Also known simply as a phage; a virus that attacks and infects bacteria. The infection may or may not lead to the death of the bacterium, depending on the phage and sometimes on conditions. Each bacteriophage is specific to one form of bacteria. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 11

Composition and Structure:

Composition and Structure Composition Nucleic acid Genome size Modified bases Protein Protection Infection Structure (T 4 ) Size Head or capsid Tail Tail Tail Fibers Base Plate Head/Capsid Contractile Sheath 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 12

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Phage entering a bacterial cell:

Phage entering a bacterial cell 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 14

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Bacteriophage showing Lytic and lysogenic cycle:

Bacteriophage showing Lytic and lysogenic cycle 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 16

Bacteriophages: Virulence Factors Carried On Phage:

Bacteriophages: Virulence Factors Carried On Phage Temperate phage can go through one of two life cycles upon entering a host cell. Lytic: Is when growth results in lysis of the host and release of progeny phage. Lysogenic: Is when growth results in integration of the phage DNA into the host chromosome or stable replication as a plasmid. Most of the gene products of the lysogenic phage remains dormant until it is induced to enter the lytic cycle. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 17

Bacteriophages: Lysogenic Conversion:

Bacteriophages: Lysogenic Conversion Some lysogenic phage carry genes that can enhance the virulence of the bacterial host. For example, some phage carry genes that encode toxins. These genes, once integrated into the bacterial chromosome, can cause the once harmless bacteria to release potent toxins that can cause disease. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 18

Bacteriophages:

Bacteriophages Used for cloning foreign genes among other applications Proteins and peptides are fused to the Capsid (surface) of the phage The combination of the phage and peptide is known as a Fusion Protein 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 19

Bacteriophages:

Bacteriophages Used for cloning foreign genes among other applications Proteins and peptides are fused to the Capsid (surface) of the phage The combination of the phage and peptide is known as a Fusion Protein 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 20

Bacteriophages:

Bacteriophages Once these Phages are isolated and recovered they can be used to infect bacteria which will create a particle similar to a monoclonal antibody 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 21

Lytic and Lysogenic cycle:

Lytic and Lysogenic cycle 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 22

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Bacteriophages: Lysogenic Conversion:

Bacteriophages: Lysogenic Conversion Examples of Virulence Factors Carried by Phage Bacterium Phage Gene Product Phenotype Vibrio cholerae CTX phage cholerae toxin cholera Escherichia coli lambda phage shigalike toxin hemorrhagic diarrhea Clostridium botulinum clostridial phages botulinum toxin botulism (food poisoning) Corynebacterium diphtheriae corynephage beta diphtheria toxin diphtheria Streptococcus pyogenes T12 erythrogenic toxins scarlet fever 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 25

Lysogenic conversion :

Lysogenic conversion In some interactions between lysogenic phages and bacteria, lysogenic conversion may occur. It is when a temperate phage induces a change in the phenotype of the bacteria infected that is not part of a usual phage cycle. Changes can often involve the external membrane of the cell by making it impervious to other phages or even by increasing the pathogenic capability of the bacteria for a host. 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 26

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Assay for Lytic Phage Plaque assay Method Plaque forming unit (pfu) Measures infectious particles Bacteria Phage + Phage Plaque assay Method Plaque forming unit (pfu) Measures infectious particles 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 27

Lytic vs Lysogenic Cycle:

Lytic vs Lysogenic Cycle 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 28

Transduction:

Transduction 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 29

Transduction:

Transduction 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 30

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31 Figure 13.10.1 Attachment: Phage attaches to host cell. Penetration: Phage pnetrates host cell and injects its DNA. Merozoites released into bloodsteam from liver may infect new red blood cells 1 2 3 Bacterial cell wall Bacterial chromosome Capsid DNA Capsid Sheath Tail fiber Base plate Pin Cell wall Tail Plasma membrane Sheath contracted Tail core 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series

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32 Figure 13.10.2 4 Maturation: Viral components are assembled into virions. Tail 5 Release: Host cell lyses and new virions are released. DNA Capsid Tail fibers 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series

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Examples: * Corynebacterium diphtheria produces the toxin of diphtheria only when it is infected by the phage β. In this case, the gene that codes for the toxin is carried by the phage, not the bacteria. * Vibrio cholerae is a non-toxic strain that can become toxic, producing cholera toxin, when it is infected with the phage CTXφ . * Clostridium botulinum causes botulism. * Streptococcus pyogenes causes scarlet fever. * Shiga toxin * Tetanus 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 33

Medical Applications of Phages:

Medical Applications of Phages “I strongly believe phage could become an effective antibacterial tool” - Carl Merril , Chief of the Laboratory of Biochemical Genetics, National Institute of Mental Health, NIH. “It might be another string on the bow, such that when (conventional antibiotics) fail, here’s something that has a chance of working. But it’s not going to be a panacea” - Joshua Lederberg, Sackler Foundation Scholar at The Rockefeller University 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 34

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The Programme Created by Dr.T.V.Rao MD for Undergraduate Learning in Developing Countries Email doctortvrao@gmail.com 11/19/2012 Dr.T.V.Rao MD's Undergraduate Series 35

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