bacterial transformation

1. PRESENTED BY- SYED AKHTAR IMAM
FMT 1ST SEM
PRESENTED TO- DR. SANGEETA
DHAWAN

2. INTRODUCTION
Transformation is the genetic alteration of a cell
resulting from the direct uptake and incorporation of
exogenous genetic material from its surroundings
through the cell membrane.
 Transformation is one of three processes for gene
transfer , in which exogenous genetic material
passes from one bacterium to another.

3.  The other two are transduction(carried out by
means of bacteriophage) & conjugation(gene is
passed through direct contact between
bacteria).
 In transformation, the genetic material passes
through the intervening medium, and uptake is
completely dependent on the recipient
bacterium.

4. Transformation

5. In this image, a gene from bacterial cell 1 is moved from bacterial cell 1 to bacterial
cell 2. This process of bacterial cell 2 taking up new genetic material is called
transformation.

6. HISTORY
 Transformation in bacteria was first demonstrated in 1928 by
the British bacteriologist Frederick Griffith.
 It was the first experiment suggesting that bacteria are
capable of transferring genetic information through a process
known as transformation. Griffith's findings were followed by
research in the late 1930s and early 40s that isolated DNA as
the material that communicated this genetic information.
 Pneumonia was a serious cause of death in the wake of the
post-WWI Spanish influenza pandemic, and Griffith was
studying the possibility of creating a vaccine. Griffith used two
strains of pneumococcus (Streptococcus pneumoniae)
bacteria which infect mice – a type III-S (smooth) which was
virulent, and a type II-R (rough) strain which was nonvirulent.

7.  The III-S strain synthesized a polysaccharide capsule that protected
itself from the host's immune system, resulting in the death of the host,
while the II-R strain did not have that protective capsule and was
defeated by the host's immune system.
 Bacteria from the III-S strain were killed by heat, and their remains were
added to II-R strain bacteria. While neither alone harmed the mice, the
combination was able to kill its host.
 Griffith was also able to isolate both live II-R and live III-S strains of
pneumococcus from the blood of these dead mice. Griffith concluded that
the type II-R had been "transformed" into the lethal III-S strain by a
"transforming principle" that was somehow part of the dead III-S strain
bacteria.
 we know that the "transforming principle" Griffith observed was the DNA
of the III-s strain bacteria. While the bacteria had been killed, the DNA
had survived the heating process and was taken up by the II-R strain
bacteria. The III-S strain DNA contains the genes that form the smooth
protective polysaccharide capsule. Equipped with this gene, the former II-
R strain bacteria were now protected from the host's immune system and
could kill the host.

10. Mechanism
o The bacterial which is able to get transformed is called
competant bacteria.
o The competant bacteria produces a protein called
competant factor.
o The competant factor molecule combines with the
plasma membrane of the bacteria binds to the cell
surface of bacteria.
o This combination causes the production of a special
type of protein called autolysin.

11. o This autolysin exposes DNA binding protein and
exonuclease present on the cell membrane of the bacteria.
o When foreign DNA comes in contact with the competant
bacterium, the DNA molecules get fragmented.
o One of the strands of the foreign DNA segment is gradually
cut into nucleotides.
o The liberated by the cut nucleotides is used for the
entrance of the other intact strand.
o The intact single strand of DNA pairs with the homologous
region of the recipient DNA of recipient bacteria.

12. o By crossing over at two sites between the homologous DNA
of donar and recipient bacteria, the foreign DNA gets
incorporated with the donar DNA.
o When such foreign DNA segment containing recipient
bacterium undergoes DNA replication, two bacteria are
produce one has original dsDNA and other has a part
foreign DNA joint to its own DNA.

15. Types of transformation
Natural transformation
o Natural transformation is a bacterial adaptation for DNA transfer
that depends on the expression of numerous bacterial genes
whose products appear to be responsible for this process.
o In general, transformation is a complex, energy-requiring
developmental process. In order for a bacterium to bind, take up
and recombine exogenous DNA into its chromosome, it must
become competent, that is, enter a special physiological state.

17. ARTIFICIAL TRANSFORMATION
 Artificial competence can be induced in laboratory
procedures that involve making the cell passively
permeable to DNA by exposing it to conditions that do not
normally occur in nature.
 Typically the cells are incubated in a solution containing
divalent cations (often calcium chloride) under cold
conditions, before being exposed to a heat pulse (heat
shock).
 Calcium chloride partially disrupts the cell membrane,
which allows the recombinant DNA enter the host cell.

18. The most common method of artificial transformation of
bacteria involves use of divalent cations (e.g., calcium
chloride) to increase the permeability of the bacterium’s
membrane, making them chemically competent, thereby
increasing the likelihood of DNA acquisition.
Another artificial method of transformation is
electroporation, in which cells are shocked with an electric
current, to create holes in the bacterial membrane. With a
newly-compromised cell membrane, the transforming DNA
is free to pass into the cytosol of the bacterium.

19. Regardless of which method of transformation is used,
outgrowth of bacteria following transformation allows
repair of the bacterial surface and selection of recombinant
cells if the newly acquired DNA conveys antibiotic
resistance to the transformed cells.