The document discusses three methods of transferring DNA between bacterial cells: conjugation, transduction, and transformation. Specifically, it states that antibiotic resistance genes are primarily spread through conjugation, which involves the transfer of DNA via cell-to-cell contact through sex pili. Additionally, several bacterial exotoxins are encoded by genes that are transferred through transduction, which is the transfer of DNA by bacteriophage. The document provides details on the mechanisms and processes of each method of horizontal gene transfer.

1. TRANSFER OF DNA
BETWEEN
BACTERIAL CELLS

2. TRANSFER OF DNA BETWEEN BACTERIAL CELLS
The transfer of genetic information from one cell to another is occur by
three methods:
# CONJUGATION
# TRANSFORMATION
# TRANSDUCTION
http://learn.genetics.utah.edu/content/microbiome/resistance/

3. Medical Viewpoint
From a medical viewpoint, the most important two consequences of
DNA transfer are:
That antibiotic resistance genes are spread from one bacterial gene
to another primarily by CONJUGATION
AND
That several important exotoxins are encoded by bacterial genes and
are transferred by TRANSDUCTION

4. CONJUGATION
Definition:
It is the process of gene transfer via sex pili between cells of opposite
mating types that are in physical contact (cell-to-cell) with each other.

5. CONJUGATION
METHODOLOGY:
Requires the presence of a special plasmid called the F plasmid.
Bacteria that have a F plasmid are referred to as F+ or male. Those that
do not have an F plasmid are F- or female.
The F plasmid consists of 25 genes that mostly code for production of
sex pilli.
A conjugation event occurs when the male cell extends his sex pilli and
one attaches to the female.
This attached pilus is a temporary cytoplasmic bridge through which a
replicating F plasmid is transferred from the male to the female.
When transfer is complete, the result is two male cells.
When the F+ plasmid is integrated within the bacterial chromosome,
the cell is called an Hfr cell (high frequency of recombination cell).

6. Conjugation in E. coli

7. Conjugation continued…

8. Conjugation continued…

9. Transduction
• Transfer of DNA by mean of bacteriophage.
• Bacterial DNA is incorporated into virus particle and is
carried into recipient cell during infection.
• Phage DNA integrated into cell DNA and cell acquire
new trait (lysogenic conversion).
• Non-pathogenic change into pathogenic.
• Diphtheria toxin, botulinum toxin, cholera toxin and
erythrogenic toxin are encoded by bacteriophages and
is transferred by transduction.

10. http://www.biologyexams4u.com/
Transduction

11. Transformation
• Transformation is a transfer of DNA from one cell to another.
• DNA is injected into the nucleus of eukaryotic cell is called
transfection.
Transfection
(used in genetic engineering procedures)
• DNA extracted from encapsulated smooth pneumococci
transform non capsulated rough pneumococci.

12. http://mmg-233-2013-genetics-genomics.wikia.com/
Transformation

13. Recombination
Once the DNA is transferred from a donor to a recipient cell by one of three
processes just described, it can integrate into host chromosome by
recombination.
Types of Recombination
There are two types of recombination:
 Homologous recombination
 Nonhomologous recombination

14. Homologous recombination, in which two pieces of DNA that have
extensive homologous regions pair up and exchange pieces of DNA by
breakage and reunion.
Homologous Recombination
https://commons.wikimedia.org/wiki/File:Homologous_recombination_in_Tn3_transposon.png

15. Nonhomologous Recombination
Nonhomologous recombination
in which little if any homology
is necessary.
http://homepage.usask.ca/~vim458/advirol/SPCV/evolution/evolution.html

16. Thank you