Natural Transformation in Gram negative bacteria

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natural transformation competence in H.influenza is induced by nutritional limitation/ starvation

expression of the genes responsible for free DNA uptake from the environment

DNA ligase integrates the foreign nucleotides into the bacterial cell DNA

transport of exogenous DNA into the bacterium is facilitated by:

assembly of DNA translocase complex at the cytoplasmic membrane

proteins that are involved in the assembly of type IV pili and type II secretion system at thye cytoplasmic membrane

Recombination is complete and the foreign DNA has integrated into the original bacterial cell’s DNA and will continue to be a part of it when the bacterial cell replicates next.

the translocated single-stranded DNA may then be integrated into the bacterial chromosomes by a RecA-dependent process

Rec A protein play a central role in homologous recombination.

RecA protein binds strongly to ssDNA to form a nucleoprotein filament. The protein has more than one DNA binding site, and thus can hold a single strand and double strand together.

catalyze a DNA synapsis reaction between a DNA double helix and a complementary region of single stranded DNA

the DNA may or may not be cleaved by the bacterial cell restriction enzyme, generating double strand breaks

the DNA uptake sequences identified is 5' AAGTGCGGT 3'

ssDNA may pass through the membrane, one strand is therefore degraded by nucleases in the process on the external surface of the cell

transport of foreign DNA from dead cell across the outer membrane:

using specialized vesicle structures (transformasomes)

into the periplasmic space

generate single strand of nucleotide that can be added to the bacterial DNA.

Natural Transformation in Gram negative bacteria

The Mechanism

DNA uptake during bacterial transformation

Definition: the bacterial adaptation for DNA transfer that depends on the expression of numerous bacterial genes which the result will carry out this process.

Haemophilus Influenza- facultatively anaerobic bacterium that can cause severe infection