a small description on conjugation in a easy form .

1. J.RISHAB
I .M.Sc BIOTECH
Conjugation :

2. INTRODUCTION :
Transfer of Genetic material from
Bacteria A to Bacteria B by Matting (or)
contact is called conjugation.
Typically , the
Genetic material
Is in form of
Plasmid (or)
A small circular
Piece of DNA.

3. HISTORY :
Discovery: Joshua Leader berg & Edward
Tatum in 1946.
They experimented with two Auxotropic strain
of E.coli denoted by Strain A and StrainB.
Strain A & Strain B were plated on minimal
medium and incubated overnight( control), no
growth observed. Also Strain A and B were
mixed together and when plated on minimal
medium resulted in prototrophs

5. Conjugation requires physical contact
• The evidence for cell to cell contact was provides by
Bernad Davis in 1950.
• On the right side is medium containing auxotrophic
strain A while on the left side is medium containing
auxotrophic strain B.
• The filter allows only the medium to move but not
the cells on either side.
• When culture was plated from both sides on
minimal medium, no prototroph growth was
observed as in Lederberg and Tatum’s experiment.

6. DONOR:


7. DURING CONJUGATION :


8. HFR CELL :
WhenF factor/ plasmid exists in an integrated
state with the host chromosome.

9. HFR ACTS :

10. STAGES DURING CONJUGATION :
1. Cell to cell contact;
2. Mobilization;
3. DNAsynthesis;
4. Separation.

11. CELL TO CELL CONTACT :
 Formation of “sex pilus” or F- bridge
between cells .

12. MOBILIZATION :
• Target DNA is replicated in F+
• Genetic transfer of ss-DNA to F-

13. DNA SYNTHESIS :
• complementary strands of DNA are replicates in both F+
and F- cells.
• Targeted DNA incorporated into F-genome.

14. SEPARATION :
• Cells separate.
• Form two F+ cells with complete
recombinant plasmids
• Both severe as donor cells for further
conjugation.