Detailed description regarding reproduction about bacteria has been mentioned with a diagrammatic presentation and wast explanation on sexual reproduction of reproduction of bacteria

1. REPRODUCTION IN BACTERIA
N.H. SHANKAR REDDY
1st Ph.D. Plant Pathology
Annamalai University

2. • Reproduction - A single bacterium divides into two daughter cells.
These are identical to the parent cell as well as to each other.
• The rate and timing of reproduction depend upon the conditions
like temperature and availability of nutrients.
• Do u know - E. coli produces about 2 million bacteria every
7 hours.

3. ASXUAL REPRODUCTION
SEXUAL REPRODUCTION

4. ASEXUAL REPRODUCTION
Binary fission
Budding
Fragmentation
Endospores

5. Binary fission
• Cell divided into similar daughter cells
by forming a constriction and cellular
material (genetic material) is equally
shared.
• A cross wall is formed between the
separating daughter chromosomes.
• This process will take 20-30 minutes

6. Budding
• A small protuberance or bud developed
at one end of the cell.
• Genome replication follows and a copy of
genome get into a bud, then bud
enlarges and eventually become a
daughter cell and finally get separated
from parent cell.

7. Fragmentation
• The multicellular organism break up
into small pieces upon maturation.
• The bacterial protoplasm undergoes
compartmentisation and form a minute
bodies called gonidia.
• Under favourable conditions each
gonidium develops into bacteria.

8. Endospores
• Resting spores produced by gram positive
bacteria (Bacillus and Clostridium) during
unfavourable conditions.
• They formed within the cells, during this
process protoplasm become concentrated
around the chromosome and hard coat formed.
• During favourable conditions spore wall
ruptures and protoplasm gives rise new
bacterium

9. SEXUAL REPRODUCTION
• Conjugation
• Transformation
• Transduction
Genetic mechanism Organism Scientist discovered Year
Conjugation E. coli Lederberg and Tatum 1946
Transformation Pneumonia Griffith 1928
Transduction Salmonella Lederberg and
Zinderberg
1952

10. Conjugation
• Conjugation was discovered by Lederberg
and Tatum in 1946 while working with
E. coli. By inducing mutation with the help
of ultraviolet and X- rays.
• They developed new strains E. coli (K12),
used as genetic markers to identify the
introduction of new characters.
• Conjugation – Transfer of genetic material
form one bacterium (donor) to another
bacterium (recipient).

11. Mechanism of conjugation
• A physical contact was involved between two
bacterium and DNA passes form one to another
through a conjugation tube. (demonstrated in E.
coli, K12)
• The donor bacterium is called F+, recipient
bacterium is called F-
• The maleness is represented as fertility factor or f
factor (f plasmid).
• ds f plasmids become two single strands and one
single stranded f plasmid moves to recipient
bacterium.
• Thus the transformed recipient cell gets new
properties like antibiotic resistance, and ability to
utilize new metabolites.
• In 1958, Lederberg, Tatum along with Beadle
received Nobel prize for explaining genetic
mechanism.

12. Transformation
• The process of gene transfer
(horizantal) by which some bacteria
take up foreign genetic material
(naked DNA) from the environment
(which is released by the donor
bacteria into external environment).
This method can be employed in
laboratory to bring out the
recombination.
• Discovered by Fred Griffith, 1928
(English bacteriologist) while
working with Pneumococcus
pneumoniae (Diplococcus).

14. Mechanism of transformation
• Bacterial transformation is based on the natural ability of bacteria to
release DNA which is then taken up by another competent bacterium.
• The fragment DNA get absorbed by the recipient bacteria and enter into
the cells.
• Inside the cell it replace the homologous part of the bacterial chromosome.
• Leads to the development of new characters of the progeny cells as stable
and heritable characters.
• Temperature and Ca, Mg ions can enhance the efficiency of
transformation.
•

15. Types of bacterial transformation
There are two forms of transformation:
Natural Transformation
• In natural transformation, bacteria naturally have the ability to
incorporate DNA from the environment directly.
• The foreign DNA attaches to the host cell DNA receptor of with the help
of DNA translocase protein and enter into host cell.
Artificial Transformation
• In the case of artificial transformation, the competence of the host cell
has to be developed artificially through different techniques.
• Chemical mediated -
• Electroporation method -

16. Transduction
• Lederberg and Zinderberg in 1952 discovered transduction principle
in Solmonella typhimurium
• Transduction – Transfer of genetic material from one bacterium to
another bacterium by the involvement of bacteriophage.
• They used same technique in which Lederberg and Tatum used,
they obtained nutritionally deficient mutants (auxotrophs) which
failed to grow on mineral medium.
• They analyses new type of genetic exchange and named as
Transduction.

18. Types of transduction
• Generalized transduction - In generalized transduction, the
bacteriophages can pick up any portion of the host's genome.
• Specialized transduction - specialized transduction, the
bacteriophages pick up only specific portions of the host's
DNA
• Abortive transduction –DNA fail to incorporate and express
individualy

20. Adsorption
Penetration
Protein synthesis
Genome synthesis
Maturation and release

22. • Transfection is the process of artificially introducing nucleic acids
(DNA or RNA) into cells, utilizing means other than viral infection.
• Purpose - Main purposes of transfection are to produce recombinant
proteins, or to specifically enhance or inhibit gene expression in
transfected cells.

23. “Wine is the most healthful and most hygienic of beverages.”
― Louis Pasteur