The document discusses bacterial conjugation, a process of genetic material transfer between bacteria via direct contact, specifically through the formation of a sex pilus. It outlines the roles of donor (F+) and recipient (F-) cells, the mechanisms of conjugation, and includes details on Hfr and F' conjugation types. Key points also mention the implications for genetic exchange, such as drug resistance and the nature of plasmids.

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2. SUBMITTED BY HAFSA ARSHAD
ROLL NO: BBOF17M006
Bs.6th Regular
SUBMITTED TO: Dr. AMIN ULLAH SHAH
DEPARTMENT OF BOTANY
UNIVERSITY OF SARGODHA

3. HISTORY
J. Lederberg and E. Tatum demonstrated
the transfer of genes between bacteria
that depends on
– direct cell to cell contact mediated by
the F pilus
– unidirectional DNA transfer from
donor to recipient
Bacterial Conjugation

4. Bacterial Conjugation
Bacterial conjugation is the transfer of genetic material
between bacterial cells by direct cell-to-cell contact or
by bridge-like connections between two cells.
 The genetic information is often beneficial to the
recipient.
 Exchange of genetic material b/w bacteria
 Physical contact required
 DNA exchanged via Pilli
 Drug resistance!!
 Horizontal Gene Transfer

5. TERMINOLOGY
The Donor
F+
Fertility factor
Contains genetic
material for gene
exchange
“ Male cell
The Recipient
F-
No fertility factor
Receives genetic material
Female cell
The Conjugate
HFR
High frequency
recombinant
Resulting genetic
recombinant
Transfers entire genomic DNA
when mixed with F- cells

6. Bacterial Plasmids
• Small, autonomously replicating DNA
molecules
– can exist independently from host
chromosome
– can integrate reversibly into the
host chromosome (episomes)
• Conjugative plasmids (F plasmid) can
transfer copies of themselves to other
bacteria during conjugation

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• F factors contain the information for
formation of sex pilus
– attach F+ cell to F- cell for DNA transfer
during bacterial conjugation
• F factors have insertion sequences (IS)
– assists in plasmid integration
Bacterial Plasmids - 2

8. 1- Cell – Cell contact
Formation of “sex pilus” or
F-bridge between cells
Attachment Via
Pilli

9. 2- MOBILIZATION
 Target DNA is replicated
in F+
 Genetic transfer of
ssDNA to F-
Genetic Transfer of ssDNA

10. F+ x F-
Mating
• A copy of the F factor is transferred to the recipient and
does not integrate into the host chromosome
• Donor genes usually not transferred
• F factor codes for sex pilus
– Type IV secretion system that makes contact between
cells that DNA moves across
• Plasmid is replicated by rolling circle method

11. HFr Conjugation
• Donor HFr cell has F factor integrated into
its chromosome
• Donor genes are transferred to recipient
cell
• A complete copy of the F factor is usually
not transferred
• Gene transfer can be clockwise
or counterclockwise

12. 3- DNA SYNTHESIS
 Complementary strands of
DNA are replicated in both
F- and F+
 Target DNA is incorporated
into F- genome
Synthesis of complimentary DNA

13. 4- SEPARATION
 Cells separate
 Form two F+ cells with
completed recombinant
plasmids
 Both serve as donor cells for
further conjugation
Separation and formation of two
F+ cells

15. F’ Conjugation
• Result when the F factor
incorrectly leaves the host
chromosome
• Some of the F factor is left
behind in the host chromosome
• Some host genes have been
removed along with some of the F
factor
– these genes can be transferred
to a second host cell by
conjugation

16. Thanks
hafsaranjha.botanist@gmail.com