2. Genetic recombination in which a DNA
fragment transferred from one bacterium
to another by a bacteriophages.
Gene transfer from a donor to a recipient
by a bacteriophages.
3. Transduction was first discovered in
1952 by Joshua Lederberg and Norton
Zinder.
He discovered this while searching for
sexual conjugation in Salmonella
species.
Norton ZinderJoshua Lederberg
4. What are Bacteriophages ?
Bacteriophages (phage) are obligate
intracellular parasites that multiply
inside bacteria by making use of
some or all of the host biosynthetic
machinery (i.e., viruses that infect
bacteria.
9. Specialized Transduction:
A DNA fragment is transferred from one
bacterium to another by a Temperate
bacteriophages which carrying donor DNA
along with Phage genome due to an error.
In this a phage insert a genome at specific
site.
10. Types of Bacteriophages
Lytic or virulent:
Phages that multiply within the host cell,
lyse the cell and release progeny phage.
Lysogenic or temperate phage:
Phage that can either multiply via the
lytic cycle or enter a quiescent state in
the bacterial cell.
• Expression of most phage genes
repressed.
• Prophage Phage DNA in the quiescent
state.
• Lysogen Bacteria harboring a prophage.
11.
12.
13. Seven steps in Generalised Transduction
1. A lytic bacteriophages adsorbs to a
susceptible bacteria.
2. The bacteriophages genome enters the
bacterium. The genome directs the
bacterium's metabolic machinery to
manufacture bacteriophages components
and enzymes.
3.Occasionally, a bacteriophages head
assembles around a fragment of donor
bacterium's nucleoid or around a plasmid
instead
of a phage genome by mistake.
14. 4. The bacteriophages are released.
5. The bacteriophages carrying the donor
bacterium's DNA adsorbs to a recipient
bacterium.
6. The bacteriophages inserts the donor
bacterium's DNA it is carrying into
the recipient bacterium.
7. The donor bacterium's DNA is
exchanged
for some of the recipient's
DNA.
17. Six steps in Specialised Transduction
1.A temperate bacteriophages adsorbs to
a susceptible bacterium and injects its
genome.
2. The bacteriophages inserts its genome
into the bacterium's nucleoid to
become a prophage.
18. 3. Occasionally during spontaneous
induction, a small piece of the donor
bacterium's DNA is picked up as part of
the phage's genome in place of
some of the phage DNA which remains in
the bacterium's nucleoid.
4.As the bacteriophages replicates, the
segment of bacterial DNA replicates
as part of the phage's genome. Every
phage now carries that segment of
bacterial DNA.
19. 5. The bacteriophages adsorbs to a
recipient bacterium and injects its
genome.
6. The bacteriophages genome carrying
the donor bacterial DNA inserts into
the recipient bacterium's nucleoid.
