2. Genetics of
Bacteria

3. Introduction
Bacterial genetics is the study of the mechanisms of
heritable information in bacteria, their chromosomes,
plasmids, transposons and phages. Techniques that
have enabled this discipline are culture in defined
media, replica plating, mutagenesis, transformation,
conjugation and transduction.

4. Bacterial Genetics
Genetics is the study of inheritance of bacterial
inherited characteristics are encoded in DNA.
Bacteria have two types of DNA that contain genes
these are:
Chromosome
Extra chromosome: Plasmid

5. Chromosome
 Bacterial chromosome is circular, double stranded DNA attached to
bacterial cell membrane.
 DNA replication in bacteria is semi-conservative .
 For example each strand of DNA is conserved intact during replication and
become one of the two strands of the new daughter molecule.

6. Plasmids
Plasmids are self- replicating extra chromosomal
DNA molecules.
It multiplies independent of the host cell.
Multiple copies of the same plasmid may be present
in each bacterial cell.
Different plasmids are also present in the same
bacterial cell.

7. Genetics Variations in Bacteria
 Bacterial genetics is the study of the mechanisms of heritable
information in bacteria, their chromosomes, plasmids,
transposons and phages. Techniques that have enabled this
discipline are culture in defined
 Transformation
 Conjugation
 transduction.

8. Transformation
 Transformation occurs when fragment of exogenous bacterial DNA are
taken up and absorbs into recipient bacterial cells. Transformation of
genes from one bacterium to another result in bacteria:
 Change in pathogenicity of the bacterium
 Change in antibiotic sensitivity
pattern of bacterium.

9. Transduction
 Transduction occurs when fragment of
chromosomal DNA is transferred into a
second bacterium by phage.
 During phage replication the bacterial
DNA may be accidently enclosed instead
of the normal phage DNA.
 When this particle which enclosed the
bacterial DNA infects a second bacterial
cell.

10. Conjugation
 Conjugation is a gene
transfer process in which a
recipient bacterium receives
DNA from a donor bacterium
by cell-to-cell contact
through conjugative pili.
Conjugation is mediated by
certain plasmids or
transposons

11. Importance
 Key role in bacterial genetics and molecular biology
 Best experimental material for molecular genetics such as
• Discovery of DNA as the carrier of genetics information
• Genetic code
• Protein synthesis
 Used to define gene structure and regulation
 First genome to be sequenced was of bacteriophage

12. Importance
Cont.
 Bacteriophage genome sequence by
• Direct sequencing of isolated bacteria
• Part of microbial genome
 Analysis of bacterial genome has shown that microbial DNA consist of
• Prophage sequence
• Prophage like element