Plasmids are circular DNA molecules that can replicate independently of the bacterial chromosome. They are usually extrachromosomal but can sometimes integrate into the bacterial chromosome. Plasmids carry several genes that are medically important, including genes for antibiotic resistance, resistance to heavy metals and ultraviolet light, and production of bacteriocins, exotoxins, pili, and fimbriae. Mechanisms of bacterial genetic exchange include conjugation, transformation, and transduction, which allow for the horizontal transfer of plasmid DNA between bacteria.

1. WHAT IS
THE PLASMID ?
Abdulmuez Abdumalek

2. WHAT IS THE PLASMID ?
Circular DNA molecules capable of replicating
Independent of the bacterial chromosome.
plasmids are usually extrachromosomal
they can be integrated into the bacterial
chromosome.

3. Plasmid

4. Clinical importance
heavy metals Resistance
as mercury which its the active component of some
antiseptics like Merthiolate
Plasmids carry the genes for the following functions
and structures of medical importance:
Antibiotic resistance

5. Clinical importance

6. Clinical importance
Resistance to ultraviolet light
which the DNA repair enzymes cause this Resistance
- Several antibiotics produced by Streptomyces
- (TB tuberculosis treatment)

7. Clinical importance
-Bacteriocins
useful in treating infections caused by antibiotic-resistant
bacteria
-Exotoxins , including several enterotoxins.

8. Pili & fimbriae
which cause the attached of bacteria to surface of Human
cells.
They have the ability to produce
disease—by enhancing colonization
on the surfaces of the cells
of other organisms.

9. Clinical importance

10. Mechanisms of Bacterial recombination
conjugation transformation transduction

11. conjugation
the exchange of genetic material takes place through
a conjugation tube between the two cells of bacteria
There are two mating types of bacteria,
1- male or donor cell ( +F )
2- female or recipient cell (-F )

12. Donor recipient
Conjugation tube

13. Donor recipient
Conjugation tube
F+

14. Donor recipient
F+

15. Transformation
‫ا‬
-Transfer of Segment DNA From one Bacteria to
another by use Bacteriophage
-Two Types : generalized and specialized

18. Transformation
Direct uptake of donor DNA by recipient cells depends on their
competence for transformation. Natural occurrence of this
property is unusual among bacteria, and some of these strains
are transformable only in the presence of competence factors,
produced only at a specific point in the growth cycle. Other
strains readily undergo natural transformation, and these
organisms offer promise for genetic engineering because of the
ease with which they incorporate modified DNA into their
chromosomes. Naturally competent transformable bacteria are
found in several genera and include Bacillus subtilis,
Haemophilus influenzae, Neisseria gonorrhoeae, and
Streptococcus pneumoniae. DNA fragments containing genes
from such organisms can be readily identified on the basis of
their ability to transform mutant cells to the wild type. These
techniques represent a substantial advance over the laborious
procedures used by Avery and his associates to demonstrate
that the pneumococcus transforming principle was DNA.
Natural transformation is an active process demanding specific

20. Reference’s
Review of Medical Microbiology and immunology 11th edition
https://microbeonline.com/bacterial-pili-fimbriae-characteristics-types
Jawetz, Melnick, & Adelberg's Medical Microbiology, 24th Edition