microbiology

1. Nafeesa Safdar
Government college university
Faisalabad,Pakistan.

2. Types of transfer of DNA between bacterial
cells

3. There are three types of transfer of genetic
material among bacterial cells.
 Conjugation
 Transduction
 Transformation

4. Why transfer of genetic material is useful?
It is important in two ways:
Antibiotic resistance genes are spread
from one generation to other by
conjugation.
Several exotoxin genes are encoded by
bacteriophage genes and are transferred
by transduction.

5. Conjugation
The mating of two bacterial cells during which DNA is
transferred from donor to recipient.
Important features:
 Fertility plasmid
 Sex pilus
 Conjugal bridge

6. How conjugation occur?
1.F plasmid
 Conjugation process is controlled by F
(fertility)plasmid.
 F plasmid carries genes for proteins that
brings out conjugation.
 The most important protein is pilin which
forms the sex pilus.

7. Mating begins:
When pilus of donor male bacterium
carrying F plasmid attaches to the receptor
on the surface of female bacterium not
carrying F plasmid.
The cells are drawn into direct contact
by” reeling in” the pilus
The F Factor is transferred .

10. High frequency recombination
Some F+ cells have their F plasmid
integrated into the bacterial DNA and
acquire the capability of transferring the
chromosome into another cell.These are
called high frequency recombition.

12. How it occurs?
In hfr transfer,the single strand of DNA that
enters the recipient F cell contains a piece
of factor at the leading end followed by
bacterial chromosome and then by the
remainder of the F factor .
Approximately 100minutes are required for
this transfer.

13. Transduction
Transduction is the transfer of cell DNA by
means of bacterial virus (bacteriophage ,
phage).
During the growth of the virus within the
cell , a piece bacterial DNA is incorporated
into the virus particle and is carried into the
recipient cell at the time of infection.
Within recipient cell ,the phage DNA is
incorporated into the cell DNA and cell
acquire new trait called lysogenic
conversion.

14. The lysogenic phage convert the
nonpathogenic organism into pathogenic
one . Diphtheria toxin botulinum toxin,
cholera toxin ,are erytherogenic toxin are
encoded by bacteriophage.

16. Types of transduction
There are two types of transduction:
1. Generalized transduction
2. Specialized transduction
Generalized transduction
It occurs when virus carries a segment from
any part of the bacterial chromosome.it
occurs 1 in every 1000 virus particles.

17. Specialized transduction
It occurs when the bacterial virus DNA that
has integrated into the cell DNA is excised
and carried with adjacent part of cell.

18. Transformation
Transfer of DNA from one cell to other itself
is called transformation.
In nautre ,dying bacteria release their DNA
,which is taken up by another recipient cell.
It is used in:
 genetic engineering
 Experiment protocols

19. Transformation

21. Transfection
When purified DNA is injected into the
nucleus of eukaryotic cell ,process called
transfection.