explanation of bacteriophages ,characters of bacteriophages, life cycles of bacteriophages, lytic and lysogenic cycle, role of bacteriophages in laboratory, phage therapy

1. BY : NIDA MAQSOOD
STUDENT

2.  a group of viruses that infect bacteria.
 also called phage or bacterial virus
 bacteriophage, meaning “bacteria eater’’

3.  Bacteriophages were discovered independently
by Frederick W Twort in Great Britain (1915)
and Félix d’Hérelle in France (1917).

4.  Thousands of varieties of phages exist
 each of which may infect only one type or a few
types of bacteria or archaea.
 a number of virus families; some examples
include Inoviridae, Microviridae, Rudiviridae,
and Tectiviridae.
 consist of a core of genetic material (nucleic
acid) surrounded by a protein capsid.
 The nucleic acid may be either DNA or RNA

6. There are three basic structural forms of phage:
an icosahedral (20-sided) head with a tail, an
icosahedral head without a tail, and a
filamentous form.

7. phage usually follows one of two life cycles,
 lytic (virulent)
 lysogenic (temperate)
1)LYTIC CYCLE:
Multiplication of phage results in cell lysis
 destroy or lyse the cell, releasing new phage particles
There are six stages in lytic cycle: attachment,
penetration, transcription, biosynthesis, maturation, and
lysis.

8. 2) LYSOGENIC CYCLE:
 Integration of phage genome into bacterial genome
 Their viral genome will integrate with host DNA
and replicate along with it fairly harmlessly, or may
established as a plasmid
 . Under certain conditions lysogenic phages can be
induced to follow a lytic cycle

10. 3) PSEUDOLYSOGENY:
 In pseudolysogeny a bacteriophage enters a cell but
neither co-opts cell-replication machinery
nor integrates stably into the host genome.

11. played an important role in laboratory research.
The T-even phages, T2, T4, and T6, were used as model
systems for the study of virus multiplication.
 lambda, Mu, and M13, are used in recombinant DNA
technology
 phage display technology for the development of human
antibody proteins
 Adalimumab (Humira), used for the treatment
of rheumatoid arthritis, was the first fully human antibody
made via phage display

12. phages being used in treating human bacterial
diseases
 such as bubonic plague and cholera.
Phage therapy was not successful, and after the
discovery of antibiotics in the 1940s, it was virtually
abandoned.
 With the rise of antibiotic-resistant bacteria,
however, the therapeutic potential of phages has
received renewed attention