explanation of bacteriophages ,characters of bacteriophages, life cycles of bacteriophages, lytic and lysogenic cycle, role of bacteriophages in laboratory, phage therapy
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
5.
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
9.
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