Bacterial Reproduction PDF

# Bacterial Conjugation ## Bacterial Conjugation - Bacterial conjugation was first discovered by Lederberg and Tatum in 1946 in Esch.coliK12 strains. ## Terminology - **The Donor (F+)**: - Contains fertility factor - Contains genetic material for gene exchange - "male" cell - **The Re...

# Bacterial Conjugation ## Bacterial Conjugation - Bacterial conjugation was first discovered by Lederberg and Tatum in 1946 in Esch.coliK12 strains. ## Terminology - **The Donor (F+)**: - Contains 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- ## Conjugation - Transfer of genetic material from Bacteria A to Bacteria B by mating or contact is called conjugation. - A diagram shows a donor bacteria with an F plasmid and a bacterial chromosome. It also has pili which attach to recipient bacteria. - The recipient bacteria also has a bacterial chromosome, but no F plasmid. ## Who is a Donor? - A diagram showing the donor and recipient bacteria shows the presence of an F-plasmid in the donor bacteria cell and its absence in the recipient cell. - **F plasmid donor (Male cell)**: F+ - **Absent recipient (Female cell)**: F- ## F Plasmid - F plasmid is also referred to as fertility factor or sex factor or transfer factor. ## Sex Pilus - A diagram shows two bacteria. One is labeled as an F- cell, and the other is labeled as an F+ cell. The F+ cell has a sex pilus connecting to the F- cell. - This F plasmid encodes for the sex pilus. ## What happens during conjugation? - A diagram shows this process with the following steps: - The donor cell attaches to the recipient cell with its pilus. - The cells connect one another. - One strand of plasmid DNA transfers to the recipient. - The recipient synthesizes a complementary strand to become an F+ cell. - The donor synthesizes a complementary strand restoring its complete plasmid. ## Once Female Recipient Cell Now Becomes Male Donor Cell - This characteristic of maleness (F+) in bacteria is transmissible or infectious. ## What is Hfr cell? - When F factor/ plasmid exists in an integrated state with the host chromosome it is called an Hfr cell. - A diagram shows a donor chromosome which integrates with the F factor/ plasmid. ## Hfr Conjugation - A diagram shows an Hfr cell. - F plasmid integrates into chromosome by recombination. - The Hfr cell then connects to an F- recipient cell through pili. - Portion of F plasmid partially moves into recipient cell trailing a strand of donor's DNA. - Conjugation ends with pieces of F plasmid and donor DNA in recipient cell. - Cells synthesize complementary DNA strands. - Donor DNA and recipient DNA recombine making a recombinant F cell. ## F+ (Free Plasmid) <=> Hfr (Integrated) - This is reversible. - **F+ (free plasmid)**: Turns an F- cell into an F+ cell upon conjugation. - **Hfr (integrated)**: Conjugation with a Hfr cell, an (F-) cell rarely becomes (F+) but it receives chromosomal DNA from the donor. ## Reversible (F+) <=> Hfr - A diagram shows the reversible relationship between the free plasmid and the integrated plasmid. ## Sexduction - When the F factor reverts from integrated free state it may sometimes carry with it some chromosomal DNA from adjacent site of its attachment. - This F factor is known as F’ factor. - A diagram shows the F- cells connecting to the F' cell to integrate the F' factor with its attached chromosomal DNA. - When (F’) conjugates with a recipient (F-), it transfers, along with the F factor, the host DNA incorporated with it. ## Medically Important Factors Which Can be Transferred by Conjugation - **Colicogenic factor (COL)** - **Resistance transfer factor (RTF)**