Bacteriophage

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Bacteriophage

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Bacteriophage

  1. 1. Bacteriophages Dr.T.V.Rao MD Dr.T.V.Rao MD
  2. 2. Bacteriophage <ul><li>A bacteriophage (from 'bacteria and Greek φαγεῖν phagein &quot;to devour&quot;) is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid. The genetic material can be ssRNA, dsRNA, ssDNA, or dsDNA ('ss-' or 'ds-' prefix denotes single-strand or double-strand) along with either circular or linear arrangement. </li></ul>Dr.T.V.Rao MD
  3. 3. 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. The lysis of the bacterial cells was said to be brought about by a virus which meant a &quot;filterable poison (&quot;virus&quot; is Latin for &quot;poison&quot;). Dr.T.V.Rao MD
  4. 4. BACTRIOPHAGES Bacteriophages typically carry only the genetic information needed for replication of their nucleic acid and synthesis of their protein coats. When phages infect their host cell, the order of business is to replicate their nucleic acid and to produce the protective protein coat. But they cannot do this alone. They require precursors, energy generation and ribosomes supplied by their bacterial host cell. Dr.T.V.Rao MD
  5. 5. Bacteriophage <ul><li>Bacteriophages make up a diverse group of viruses, some of which have complex structures, including double-stranded DNA. </li></ul>Dr.T.V.Rao MD
  6. 6. Bacteriophage Dr.T.V.Rao MD
  7. 7. Bacteriophage <ul><li>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. </li></ul>Dr.T.V.Rao MD
  8. 8. Bacteriophages: Classification <ul><li>At present, over 5000 bacteriophages have been studied by electron microscopy and can be divided into 13 virus families. </li></ul>Dr.T.V.Rao MD
  9. 9. Double stranded DNA, Enveloped Double stranded DNA, Non-enveloped Myoviridae Siphoviridae Podoviridae P2 T2 λ P22 Tectiviridae PRD1 Corticoviridae PM2 Single-stranded DNA Inoviridae M13 & fd Microviridae Φ X174 Leviviridae Single stranded RNA MS2 Lipothrixviridae TTV1 Fuselloviridae SSV1 Plasmaviridae Double stranded RNA phi6 66 Cystoviridae Rudiviridae SIRV 1, 2 13 Bacteriophage families Dr.T.V.Rao MD
  10. 10. 13 Bacteriophage families Dr.T.V.Rao MD Corticoviridae icosahedral capsid with lipid layer, circular supercoiled dsDNA Cystoviridae enveloped, icosahedral capsid, lipids, three molecules of linear dsRNA Fuselloviridae pleomorphic, envelope, lipids, no capsid, circular supercoiled dsDNA Inoviridae genus (Inovirus/Plectrovirus) long filaments/short rods with helical symmetry, circular ssDNA Leviviridae quasi-icosahedral capsid, one molecule of linear ssRNA Lipothrixviridae enveloped filaments, lipids, linear dsDNA Microviridae icosahedral capsid, circular ssDNA Myoviridae (A-1,2,3) tail contractile, head isometric Plasmaviridae pleomorphic, envelope, lipids, no capsid, circular supercoiled dsDNA Podoviridae (C-1,2,3) tail short and noncontractile, head isometric Rudiviridae helical rods, linear dsDNA Siphoviridae (B-1,2,3) tail long and noncontractile, head isometric Tectiviridae icosahedral capsid with, linear dsDNA, &quot;tail&quot; produced for DNA injection
  11. 11. Bacteriophages <ul><li>  Morphology of the T series of Phages </li></ul>Name Plaque size Head (nm) Tail (nm) Latent period (min) Burst size T1 medium 50 150 x 15 13 180 T2 small 65 x 80 120 x 20 21 120 T3 large 45 invisible 13 300 T4 small 65 x 80 120 x 20 23.5 300 T5 small 100 tiny 40 300 T6 small 65 x 80 120 x 20 25.5 200-300 T7 large 45 invisible 13 300
  12. 12. Dr.T.V.Rao MD
  13. 13. Cycle of events in Bacteriophage infecting a Bacterial Cell Dr.T.V.Rao MD
  14. 14. Phage entering a bacterial cell Dr.T.V.Rao MD
  15. 15. Dr.T.V.Rao MD
  16. 16. Lytic and Lysogenic cycle Dr.T.V.Rao MD
  17. 17. Bacteriophages: Virulence Factors Carried On Phage <ul><li>Temperate phage can go through one of two life cycles upon entering a host cell. </li></ul><ul><ul><li>Lytic: </li></ul></ul><ul><ul><li>Is when growth results in lysis of the host and release of progeny phage. </li></ul></ul><ul><ul><li>Lysogenic: </li></ul></ul><ul><ul><li>Is when growth results in integration of the phage DNA into the host chromosome or stable replication as a plasmid. </li></ul></ul><ul><ul><li>Most of the gene products of the lysogenic phage remains dormant until it is induced to enter the lytic cycle. </li></ul></ul>Dr.T.V.Rao MD
  18. 18. Dr.T.V.Rao MD
  19. 19. Lysogenic conversion In some interactions between lysogenic phage's 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. Dr.T.V.Rao MD
  20. 20. Examples: of Lysogenic conversion * 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 cholera 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 Dr.T.V.Rao MD
  21. 21. Bacteriophages: Lysogenic Conversion <ul><li>Examples of Virulence Factors Carried by Phage </li></ul>Dr.T.V.Rao MD 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
  22. 22. Bacteriophages Uses <ul><li>Used for cloning foreign genes among other applications </li></ul><ul><li>Proteins and peptides are fused to the Capsid (surface) of the phage </li></ul><ul><li>The combination of the phage and peptide is known as a Fusion Protein </li></ul>Dr.T.V.Rao MD
  23. 23. Bacteriophages causes Lysis of Infected Cells <ul><li>The T-phages, T1 through T7,  are referred to as lytic phages because they always bring about the lysis and death of their host cell, the bacterium  E. coli . T-phages contain double-stranded DNA as their genetic material. In addition to their protein coat or capsid (also referred to as the &quot;head&quot;), T-phages also possess a tail and some related structures </li></ul>Dr.T.V.Rao MD
  24. 24. Dr.T.V.Rao MD
  25. 25. Genetic Engineering Bacteriophages <ul><li>Different sets of genes are inserted into the genomes of multiple phages </li></ul><ul><li>These separate phages will only display one protein, peptide, or antibody </li></ul><ul><li>Collections of these phages can comprise Libraries </li></ul><ul><li>These Libraries are exposed to selected targets and only some phages will interact with targets </li></ul>Dr.T.V.Rao MD
  26. 26. Bacteriophages Dr.T.V.Rao MD
  27. 27. Bacteriophages <ul><li>Once these Phages are isolated and recovered they can be used to infect bacteria which will create a particle similar to a monoclonal antibody </li></ul>Dr.T.V.Rao MD
  28. 28. Bacteriophages <ul><li>By taking gene segment of antigens of antibodies and fusing them to the protein coat of phages, these phages will now express the anti-body in a fusion protein </li></ul><ul><li>Phage Display Libraries of antigens can be created to create anti-body phage display libraries </li></ul>
  29. 29. Bacteriophages in Medicine <ul><li>Bacteriophages, or phages, by their very nature, they can be considered as potential antibacterial agents. Over the past decade or two, the idea of phage therapy, i.e. the use of lytic bacteriophages for both the prophylaxis and the treatment of bacterial infections, has gained special significance in view of a dramatic rise in the prevalence of highly antibiotic-resistant bacterial strains paralleled by the withdrawal of the pharmaceutical industry from research into new antibiotics </li></ul>Dr.T.V.Rao MD
  30. 30. Phage Therapy <ul><li>Phages were discovered to be anti-bacterial agents and were used throughout the 1940s in the Soviet Union for treating bacterial infections. They had widespread use including treating soldiers in the Red Army. However, they were abandoned for general use in the west for several reasons: </li></ul>Dr.T.V.Rao MD
  31. 31. Phage Therapy <ul><li>Medical trials were carried out, but a basic lack of understanding of phages made these invalid. </li></ul><ul><li>Phage therapy was seen as untrustworthy, because many of the trials were conducted on totally unrelated diseases such as allergies and viral infections. </li></ul>Dr.T.V.Rao MD
  32. 32. FDA Approves <ul><li>In August 2006, the United States Food and Drug Administration (FDA) approved LMP-102 (now List Shield) as a food additive to target and kill Listeria monocytogenes . LMP-102 was approved for treating ready-to-eat (RTE) poultry and meat products. In October of that year, following the food additive approval of LMP-102 by Intralytix, the FDA approved a product by EBI using bacteriophages on cheese to kill the Listeria monocytogenes bacteria, giving them GRAS status. </li></ul>Dr.T.V.Rao MD
  33. 33. <ul><li>Programme created by Dr.T.V.Rao MD Medical and Paramedical Students in the Developing World </li></ul><ul><li>Email </li></ul><ul><li>[email_address] </li></ul>Dr.T.V.Rao MD

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