bacteriophage overview

1. Bacteriophage
By
Mohammed Abdulkadhim

2. • Define
• Discovery of bacteriophage
• Types of bacteriophage
• Structure of bacteriophage
• Life cycle
• Questions

3. Define
• Bacteriophages: are viruses that can infect and destroy bacteria.
• Obligate intracellular parasites
• Most bacteriophages are specific to one form of bacteria
• Some bacteriophages have ability to infect strains from either different
genera or species called Polyvalent phages
• They present widely in nature (soil, water)

4. Discovery of bacteriophage
Bacteriophage observed in 1915 by British bacteriologist “Twort”
Then discovery by Canadian bacteriologist “Félix d’Herelle” in 1917 at
the Pasteur Institute in France and coined the term “Bacteriophage”
which means “eaters of bacteria”

5. Types of bacteriophage
• Bacteriophages are estimated there are more than 1031 bacteriophages on the earth
• More than 6000 different bacteriophages have been discovered and described
morphologically
• T-even phages such as T2, T4 and T6 that infect E.coli
• Bacteriophages are generally divided into two basic classes, virulent and temperate

6. Structure of bacteriophage
• Bacteriophage have
genetic material in the
form of either DNA or
RNA, encapsulated by a
protein coat called capsid
that is attached to a tail

7. Life cycle
1. Adsorption: The first step in the infection process is the adsorption of
the phage to the bacterial cell. Phages attach to specific receptors on the
bacterial cell such as proteins on the outer surface of the bacterium,
LPS, pili, and lipoprotein.
2. Penetration: the tail is forced to penetrate the weakened cell wall and
come into contact with the bacterial cell membrane, The viral DNA
then moves from the head through the tube into the bacterial cell.

9. Life cycle
3. Synthesis: Once the phage DNA enters the host cell ,phage genes take
control of the host cell’s metabolic machinery.
4. Maturation: The assembly of phage components into mature infective
phage particle.
5. Release: The enzyme lysozyme is breaks down the cell wall, allowing
viruses to escape, The released phages can now infect more susceptible
bacteria

10. Life cycle

12. Questions
• What are Bacteriophages?
• What is structure of bacteriophage?
• Can bacteriophage be used as therapy?

13. References
• Black, J. G., and Black, L. J. (2015). Microbiology: principles and
explorations. John Wiley & Sons. 940 pp.
• Lenski, R. E. (1988). Dynamics of interactions between bacteria and
virulent bacteriophage. In Advances in microbial ecology (pp. 1-44).
Springer, Boston, MA.
• Wittebole, X., De Roock, S., and Opal, S. M. (2013). A historical overview
of bacteriophage therapy as an alternative to antibiotics for the treatment of
bacterial pathogens. Virulence, 5(1), 226–235.
https://doi.org/10.4161/viru.25991