TRANSFER OF DNA

BETWEEN BACTERIAL

CELLS

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/

Medical ViewpointFrom 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 CONJUGATIONAND

That several important exotoxins are encoded by bacterial genes and are transferred by TRANSDUCTION

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.

CONJUGATIONMETHODOLOGY: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).

Conjugation in E. coli

Conjugation continued…

Conjugation continued…

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.

http://www.biologyexams4u.com/

Transduction

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.

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

Transformation

RecombinationOnce 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

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

Nonhomologous Recombination

Nonhomologous recombination in which little if any homology is necessary.

http://homepage.usask.ca/~vim458/advirol/SPCV/evolution/evolution.html

Thank you