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1. Microbiology -18BT32
Topic – Reproduction in Bacteria
Prepared & presented by:
Ms.Salma kausar M
Assistant professor
Dept. of BT
TOCE,bangalore

2. Introduction
• The production of new individuals by the existing
ones is called reproduction.
• There are two quite distinct methods of producing
offsprings viz., asexual and sexual methods.
• The asexual reproduction involves a single parent
and produces offsprings which are genetically
identical to the parent.
• The sexual reproduction involves genetic
recombination between two parents and so
produces offsprings which differ not only from the
parent but also from each other.

3. Reproduction in bacteria
Bacteria reproduce by vegetative, Asexual & sexual
method
1. Vegetative method: binary fission, budding,
fragmentation
2. Asexual method: endospore formation
3. Sexual method: it occurs through genetic
recombination viz; transformation, conjugation
and transduction.

4. Vegetative method
1. Binary fission: In binary fission, single cell
divides into two equal cells .
• Initially the bacterial cell reaches a critical mass in
its structure and cellular constituents.
• The circular double stranded DNA of bacteria
undergoes replication, where both the strands
separate and new complementary strands are
formed on the original strands.
• resulting in the formation of two identical double
stranded DNA

5. BINARY FISSION
BUDDING
FRAGMENTATION

6. 2. Budding: The bacterial cell develops small
swelling at one side which gradually increases in
size.
• Simultaneously the nucleus undergoes division,
where one remains with the mother and other
one with some cytoplasm goes to the swelling.
• This outgrowth is the bud, which gets separated
from the mother by partition wall
3. Fragmentation: It occurs in colonial
cyanobacteria.
• After reaching a certain length, the blue
bacterium breaks up into pieces called fragments.
Each fragment is the beginning of a new colony.

7. Asexual method
Endospore formation
• Spores are formed
during unfavourable
environmental condition
like desiccation and
starvation.
• As the spores are
formed within the cell,
they are called
endospores.
• Only one spore is
formed in a bacterial
cell.
• On germination, it gives
rise to a bacterial cell

8. Sexual method
• Cytological observations and genetic studies
indicate that something like sexual reproduction,
involving the fusion of two different cells and a
transfer of hereditary factors, occurs in
bacteria,although infrequently.
• But, typical sexual reproduction through the
agency of gametes is absent in bacteria.
• There is no fertilization and meiosis.
• However, the gene transfer in bacteria occurs by
three methods—Transformation, Conjugation,
and Transduction.

9. Transformation
• Frederick Griffith (1928), an English bacteriologist,
accidently found that the heat-killed bacteria of
virulent strain (type) of Pneumococcus
pneumoniae could transfer characteristics of its
strain to the non-virulentstrain of living bacteria

10. Mechanism of transformation
1.Competency
2.Binding
3.Penetration
4.Synapis
5.Integration
6.Covalant linkage

11. Conjugation
• Conjugation involves transfer
of DNA from a donor or male
cell to a recipient or female
cell through a specialized sex
pilus or conjugation tube.
1-Donor cell produces pilus.
2-Pilus attaches to recipient cell,
brings the two cells together.
3-The mobile plasmid is nicked and
a single strand of DNA is then
transferred to the recipient cell.
4-Both cells recircularize
theirplasmids, synthesize second
strands, and reproduce pili;
both cells are now viable donors.

12. Conjugation between Hfr male and F- female
• The F factor can integrate into
the host chromosome.
• An F+ cell carrying an
integrated F factor is called an
Hfr(for high-frequency
recombination).
• Therefore, the F+ male
becomes Hfr male.
• In the integrated state, the F
factor mediates the transfer of
a chromosome of the Hfr male
cell to a recipient (F-) cell.
• Usually only a portion of the
Hfr chromosome is transferred
before the cells separate, thus,
breaking the chromosome.

13. Transduction
• It was first discovered by N. Zinder and J. Lederberg in 1952, in
Salmonella typhimurium, a mouse typhoid bacterium.
Transduction is the transfer of DNA from a donor cell to a
recipient cell by bacteriophages. In most cases only a small
segment of the host (i.e. the donor) DNA is transferred.

14. Mechanism of transduction

15. Questions?????????????