Bacteriophage, Phage
Typing and Application
By:- Zebene A.
Out line of the presentation
 Introduction
 Composition and Structure of Bacteriophages
 Infection of Host Cells
 Phag...
Introduction
 Bacteriophage
 Virus that infects bacteria.
 Obligate intracellular parasites that multiply
inside bacter...
Diversity
 There are at least 12 distinct groups of
bacteriophages
 which are very diverse structurally and
genetically;...
Composition and Structure of Bacteriophage
A. Composition
 They all contain nucleic acid and protein.
 Depending upon th...
B. Structure
Bacteriophages come in many different sizes and
shapes.
 Size - T4 is among the largest phages; it is
approx...
 Tail-Many but not all phages have tails
attached to the phage head.
 Is a hollow tube through which the nucleic
acid pa...
Structure of Enterbacteriacae
phage/Bacteriophage T4
Infection of Host Cells
A. Adsorption
 Mediated by the tail fibers or by some analogous
structure on those phages that la...
B. Irreversible attachment
 The attachment of the phage to the bacterium via
the tail fibers is a weak one and is reversi...
C. Sheath Contraction
 The irreversible binding of the phage to the
bacterium results in the contraction of the
sheath (f...
Phage Multiplication Cycle
 Based on the multiplication cycle /event occur
during replication:-
A. Lytic or Virulent Phag...
A. Lytic or Virulent Phages
 Lytic or virulent phages are phages which can
only multiply on bacteria and kill the cell by...
Lytic cycle
B. Lysogenic cycle/Temperate
 Either multiply via the lytic cycle or enter a
quiescent state in the cell
 In this quiesc...
Events Leading to Lysogeny:-The Prototype
Phage: Lambda
1. Circularization of the phage chromosome
2. Site-specific recomb...
What determines whether the virus takes
Lytic or Lysogenic cycle?
 Determined by the concentration of the
repressor and a...
Events Leading to Termination
of Lysogeny
 Anytime a lysogenic bacterium is exposed to
adverse conditions, the lysogenic ...
General cycle In the lysogeny
 Used for identification and differentiating of
bacterial pathogen.
 Specific bacteriophage isolated is mixed with
known...
Plaque assay/Assay for Lytic Phage
 Lytic phages are enumerated by a plaque
assay
 A plaque is a clear area which result...
Application of Bacteriophages
 Model for animal virus transformation
 Lysogeny is a model system for virus
transformatio...
Cont’d
 Phage Therapy
 Can any phage be used for developing
therapeutic phage preparation?
 Environmental Applications
...
Reference
1. Microbiology byte [Internet].[Last updated 2010, cited 2013]
http://www.microbiologybytes.com/virology/Phages...
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Bacteriophage, phage typing and application

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  • 1. Eclipse period During the eclipse phase, no infectious phage particles can be found either inside or outside the bacterial cell. The phage nucleic acid takes over the host biosynthetic machinery and phage specified m-RNA's and proteins are made. There is an orderly expression of phage directed macromolecular synthesis, just as one sees in animal virus infections. Early m-RNA's code for early proteins which are needed for phage DNA synthesis and for shutting off host DNA, RNA and protein biosynthesis. In some cases the early proteins actually degrade the host chromosome. After phage DNA is made late m-RNA's and late proteins are made. The late proteins are the structural proteins that comprise the phage as well as the proteins needed for lysis of the bacterial cell.2. Intracellular Accumulation Phase In this phase the nucleic acid and structural proteins that have been made are assembled and infectious phage particles accumulate within the cell.3. Lysis and Release Phase After a while the bacteria begin to lyse due to the accumulation of the phage lysis protein and intracellular phage are released into the medium. The number of particles released per infected bacteria may be as high as 1000.
  • The cell harboring a prophage is not adversely affected by the presence of the prophage and the lysogenic state may persist indefinitely.
  • Bacteriophage, phage typing and application

    1. 1. Bacteriophage, Phage Typing and Application By:- Zebene A.
    2. 2. Out line of the presentation  Introduction  Composition and Structure of Bacteriophages  Infection of Host Cells  Phage Multiplication Cycle  A. Lytic or Virulent Phages  B. Lysogenic or Temperate Phage  Phage Typing  Application of Bacteriophages  Reference
    3. 3. Introduction  Bacteriophage  Virus that infects bacteria.  Obligate intracellular parasites that multiply inside bacteria by making use of some or all of the host biosynthetic machinery.  Twort and d'Herelle in 1915 and 1917  broth cultures of certain intestinal bacteria could be dissolved by addition of a bacteria-free filtrate obtained from sewage.
    4. 4. Diversity  There are at least 12 distinct groups of bacteriophages  which are very diverse structurally and genetically;  the best known ones are the common phages of E.coli:T4(lytic phage )&Lambda Phage(Lysogenic phage)  Phage Diversity.docx
    5. 5. Composition and Structure of Bacteriophage A. Composition  They all contain nucleic acid and protein.  Depending upon the phage, the nucleic acid can be either DNA or RNA but not both.  Complexity vary from 3-5 average size gene products code for over 100 gene  The nucleic acids of phages often contain unusual or modified bases.  These modified bases protect phage nucleic acid from nucleases that break down host nucleic acids during phage infection.
    6. 6. B. Structure Bacteriophages come in many different sizes and shapes.  Size - T4 is among the largest phages; it is approximately 200 nm long and 80-100 nm wide. Other phages are smaller. Most phages range in size from 24-200 nm in length.  Head or Capsid -All phages contain a head structure which can vary in size and shape.  Head acts as the protective covering for the nucleic acid.
    7. 7.  Tail-Many but not all phages have tails attached to the phage head.  Is a hollow tube through which the nucleic acid passes during infection.  size of the tail can vary  E.g. Complex phages like T4  The tail is surrounded by a contractile sheath which contracts during infection of the bacterium  At the end the tail have a base plate and one or more tail fibers involved in the binding of the phage to the bacterial cell.
    8. 8. Structure of Enterbacteriacae phage/Bacteriophage T4
    9. 9. Infection of Host Cells A. Adsorption  Mediated by the tail fibers or by some analogous structure on those phages that lack tail fibers and it is reversible.  The tail fibers attach to specific receptors on the bacterial cell and the host specificity of the phage  The nature of the bacterial receptor varies for different bacteria(proteins on the outer surface of the bacterium, LPS, Pili, and lipoprotein)
    10. 10. B. Irreversible attachment  The attachment of the phage to the bacterium via the tail fibers is a weak one and is reversible.  Irreversible binding of phage to a bacterium is mediated by one or more of the components of the base plate.  Phages lacking base plates have other ways of becoming tightly bound to the bacterial cell.
    11. 11. C. Sheath Contraction  The irreversible binding of the phage to the bacterium results in the contraction of the sheath (for those phages which have a sheath) and the hollow tail fiber is pushed through the bacterial envelope. D. Nucleic Acid Injection  The DNA/RNA ejected to the bacterial cell through the hollow tube  The remainder of the phage remains on the outside of the bacterium
    12. 12. Phage Multiplication Cycle  Based on the multiplication cycle /event occur during replication:- A. Lytic or Virulent Phages B. Lysogenic or Temperate Phage
    13. 13. A. Lytic or Virulent Phages  Lytic or virulent phages are phages which can only multiply on bacteria and kill the cell by lysis at the end of the life cycle.  Life cycle  1. Eclipse period  2. Intracellular Accumulation Phase  3. Lysis and Release Phase
    14. 14. Lytic cycle
    15. 15. B. Lysogenic cycle/Temperate  Either multiply via the lytic cycle or enter a quiescent state in the cell  In this quiescent state most of the phage genes are not transcribed  Phage DNA in the repressed state is called a prophage because it is not a phage but it has the potential to produce phage.  The cell harboring a prophage is termed a lysogen.
    16. 16. Events Leading to Lysogeny:-The Prototype Phage: Lambda 1. Circularization of the phage chromosome 2. Site-specific recombination 3. Repression of the phage genome  A phage coded protein, called a repressor, is made which binds to a particular site on the phage DNA, called the operator, and shuts off transcription of most phage genes except the repressor gene.
    17. 17. What determines whether the virus takes Lytic or Lysogenic cycle?  Determined by the concentration of the repressor and another phage protein called cro in the cell.  If a promoter of repressor gene called C I dominates the phage will progress to lysogenic.  If the an operator gene called cro dominates the phage will progress to lytic cycle.
    18. 18. Events Leading to Termination of Lysogeny  Anytime a lysogenic bacterium is exposed to adverse conditions, the lysogenic state can be terminated. This process is called induction  Adverse conditions lead to the production of proteases (rec A protein) which destroy the repressor protein.  This in turn leads to the expression of the phage genes, reversal of the integration process and lytic multiplication
    19. 19. General cycle In the lysogeny
    20. 20.  Used for identification and differentiating of bacterial pathogen.  Specific bacteriophage isolated is mixed with known bacterial pathogen  The lysis due to viral infection of the bacterium is specific and important in identification of the host. Phage Typing
    21. 21. Plaque assay/Assay for Lytic Phage  Lytic phages are enumerated by a plaque assay  A plaque is a clear area which results from the lysis of bacteria.  Each plaque arises from a single infectious phage.  The infectious particle that gives rise to a plaque is called a pfu (plaque forming unit).
    22. 22. Application of Bacteriophages  Model for animal virus transformation  Lysogeny is a model system for virus transformation of animal cells  Bacteriophage-based Diagnostics and Phage Typing  Phage as vehicles for vaccine delivery  Phage display  A molecular technique used in synthesizing polypeptides with novel characteristics.
    23. 23. Cont’d  Phage Therapy  Can any phage be used for developing therapeutic phage preparation?  Environmental Applications  Bio control for dangerous bacteria
    24. 24. Reference 1. Microbiology byte [Internet].[Last updated 2010, cited 2013] http://www.microbiologybytes.com/virology/Phages.html 2. University of South Carolina School of Medicine: Microbiology and Immunology on line [Internet].[Last updated 2010, cited 2013] Available from http://pathmicro.med.sc.edu/mayer/phage.htm 3. Kenneth Todar.The Microbial WorldLectures in Microbiology by Kenneth Todar PhD University of Wisconsin-Madison Department of Bacteriology [Internet]. [Last updated 2012, cited 2013] Available from http://textbookofbacteriology.net/themicrobialworld/Phage.html 4. Madigan, Martinko, Stahl, Clark. Brock Biology of Microorganisms 13thEdition: Virus and Virology: Pearson Education .Inc; 2008. 5. Elisabeth Kutter, Alexander Sulakvelidze. Bacteriophage Biology and Application: CRC Press; 2005. 6. Irshad Ul Haq, Waqas Nasir Chaudhry, Maha Nadeem Akhtar, Saadia Andleeb and Ishtiaq Qadri. Bacteriophages and their implications on future biotechnology: a review. Virology Journal 2012; 9(9);1-8 7. Filippov AA, Sergueev KV, Nikolich MP (2013) Bacteriophages against Biothreat Bacteria: Diagnostic, Environmental and Therapeutic Applications. J Bioterr Biodef 2013, S3 : 1-8.

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