Bacteria undergo genetic exchange through three main processes: transformation, transduction, and conjugation. Transformation involves the uptake of naked DNA by bacteria. Transduction occurs when bacterial DNA is transferred between cells inside bacteriophage particles. Conjugation allows direct transfer of genetic material through cell-to-cell contact via plasmids or sex pili. These processes allow bacteria to acquire new genes horizontally and contribute to the genetic diversity and evolution of bacterial populations.

1. BACTERIAL GENETICS
NIAYESH FORGHANI & NILOOFAR AMINAN
OCTOBER 2016

4. BACTERIA: PROKARYOTES
• nucleoid : not enclosed by nuclear membrane
• most have one circular chromosome consisting of double-
stranded DNA
• single origin of bidirectional replication
• Note: When straightened, the length of DNA 1000µm but
usually expressed as kilobases (1000 base pairs)
• Bacterial DNA is 4000kb whereas Human genome is 3 million
kb long

6. BINARY FISSION

8. EXTRACHROMOSOMAL GENETIC ELEMENTS :
PLASMID
• Plasmids are circular DNA molecules present in cytoplasm of
bacteria, capable of autonomous replication.
• Important vectors for Genetic engineering
• Plasmid DNA may be integrated with chromosomal DNA. Such
integrated forms are called Episomes.
• Carry genetic information for new bacterial properties e.g. virulence
factors and anti biotic resistance.
• May transfer from one cell to another ( conjugative plasmids ).

10. Episome

11. PLASMID TYPING
• Col plasmids. These plasmids contain genes that code for bacitracin's, proteins
that can kill other bacteria.
• F-plasmid (Fertility plasmids) contain tragenes and are capable of conjugation
resulting in the expression of sex pilli.
• Resistance plasmids.

12. BACTERIAL GENETIC DIVERSITY
• Mutation
• Genetic Recombination (Gene transfer or
Exchange)

13. MUTATION
• definition: any change in the base sequence of DNA
• Types of mutation : single base change & frameshift
mutation

14. SINGLE BASE CHANGE

15. FRAMESHIFT MUTATION

16. THREE PROCESSES BRING BACTERIAL DNA
FROM DIFFERENT INDIVIDUALS TOGETHER
• Transformation
• Transduction
• Conjugation

17. TRANSFORMATION
• Transfer of genetic information through the agency of free
DNA
• Griffith 1928 – Mice – Experimental inoculation of
Streptococcus pneumoniae – (R) forms Live non-capsular
strain type II, (S) forms Heat-Killed capsular type III strain
Isolated from Blood culture of Mice. Showed transfer of
information of capsule synthesis from heat killed to live strain
was demonstrated invitro also.

19. TRANSDUCTION
• Transfer of bacterial DNA from one cell to another by
means of a bacteriophage infection .
• Chromosomal DNA, Plasmid, Episomes can be transduced,

20. TRANSDUCTION TYPES
• Generalized transduction : random packaging of bacterial
host cell DNA in phage capsid.
• Specialized transduction : when prophage genome is
excised it drags adjacent bacterial genes resulting in
hybrid phage-bacterial genome.

23. BACTERIOPHAGES EXHIBITS 2 TYPES OF LIFE CYCLE.
• A. Virulent or Lytic, B. Lysogenic

24. TRANSDUCTION HAS SOME BENEFITS
• In transduction --- Phage is a carrier of genetic material from one bacteria to
another
• In Lysogenic conversion --- Phage itself is a new genetic element to the host
bacterium
• Susceptibility to bacteriophages (Immunity to superinfection with same or
related phages)

25. CONJUGATION
• Conjugation or Sexduction is a process whereby a male cell or donor
bacterium mates or makes physical contact with female cell or recipient
bacterium and transfers genetic elements into it.
• Plasmids are frequently transferred by conjugation; and it was in E.coli K12
the role of plasmids in conjugation was first recognized.
• “Maleness” Contains F (fertility) genes on plasmid or in genome. Encoded sex
pilus (Conjugation tube)- Forms passage way for DNA from donor to recipient

27. F FACTOR
• Transfer factor that contains
the genetic information
necessary for synthesis of Sex
Pilus and for self transfer
without any other identifiable
genetic materials such as drug
resistance

32. TRANSPOSONS
• Structurally / Genetically – Discrete sequence of DNA – Move around in a cut
and paste manner between Chromosomal and Extra chromosomal DNA
molecules within cells.
• Transposons or Jumping genes
• Mode of gene transfer
• Transposition – a mechanism for amplifying genetic transfer in nature
• Small Transposons 1 – 2 Kb
• Not self replicating and depend on Plasmid or Chromosome for replication.
• A chunk of DNA is added by Transposons.
• Barbara Mc Clintock

36. SOURCE
NREVIEW OF MEDICAL MICROBIOLOGY >
JAWETZ , MELNIK & ADELBERG