A bacteriophage is a type of virus that infects bacteria. In fact, the word "bacteriophage" literally means "bacteria eater," because bacteriophages destroy their host cells. All bacteriophages are composed of a nucleic acid molecule that is surrounded by a protein structure

1. Bacteriophages
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2. Bacteriophage
 A bacteriophage (from 'bacteria and
Greek φαγεῖν phagein "to devour") 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.
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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 "filterable poison
("virus" is Latin for "poison").
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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.
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5. Bacteriophage
 Bacteriophages
make up a
diverse group of
viruses, some of
which have
complex
structures,
including double-
stranded DNA.
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6. Bacteriophage
 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.
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7. Double stranded
DNA, Enveloped
Double stranded DNA,
Non-enveloped
Siphoviridae
Podoviridae
P2
Myoviridae
T2
λ
P22
Tectiviridae PRD1
Corticoviridae
PM2
Single-stranded DNA
Inoviridae
M13 & fd
Microviridae ΦX174
Single
stranded
RNA
MS2
Lipothrixviridae
TTV1
Fuselloviridae SSV1
Plasmaviridae
Double
stranded
RNA
phi666
Cystoviridae
Rudiviridae
SIRV 1, 2
13 Bacteriophage families
Dr.T.V.Rao MDLeviviridae 9
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8. Cycle of events in Bacteriophage
infecting a Bacterial Cell
88

9. Phage entering a bacterial cell
99

10. 10
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11. Lytic and Lysogenic cycle
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1
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12. Bacteriophages:

Virulence Factors Carried On Phage
Temperate phage can go through one of two life cycles
upon entering a host cell.
1) Lytic:
Is when growth results in lysis of the host and release of progeny
phage.
3) Lysogenic:
Is when growth results in integration of the phage DNA into the
host chromosome or stable replication as a plasmid.
Most of the gene products of the lysogenic phage remains
dormant until it is induced to enter the lytic cycle.
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2

13. 13
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14. 14
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.
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15. 15
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
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16. Phage structure

17. Life cycle of bacteriophage T4

18. Bacteriophages:
Lysogenic Conversion
Examples of Virulence Factors Carried by Phage
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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
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19. Bacteriophages Uses
•
•
•
Used for cloning foreign
genes among other
applications
Proteins and peptides are
fused to the
Capsid(surface) of the
phage
The combination of the
phage and peptide is
known as a Fusion Protein
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20. 20
Bacteriophages causes Lysis of
Infected Cells
 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 "head"), T-phages also possess a tail
and some related structures
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21. Genetic Engineering
Bacteriophages
•
•
•
•
Different sets of genes are
inserted into the genomes
of multiple phages
These separate phages will
only display one protein,
peptide, or antibody
Collections of these phages
can comprise Libraries
These Libraries are
exposed to selected
targets and only some
phages will interact wD
it
r.T
h
.V.Rao MD
targets
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22. Bacteriophages
• Once these Phages are isolated and
recovered they can be used to infect
bacteria which will create a particle
similar to a monoclonal antibody
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23. Bacteriophages
•
•
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
Phage Display Libraries of
antigens can be created to
create anti-body phage
display libraries 2
3

24. Bacteriophages in Medicine
 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
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25. Phage Therapy
 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:
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26. Phage Therapy


Medical trials were
carried out, but a basic
lack of understanding of
phages made these
invalid.
Phage therapy was seen
as untrustworthy,
because many of the
trials were conducted on
totally unrelated diseases
such as allergies and
viral infections.
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27. FDA Approves
 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.
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