Bacillus Plasmids

Bacillus Plasmids

Bacillus Plasmids
Bacteriocins are protein toxins produced by certain bacteria which inhibit the growth of related bacteria but are not effective against those which produce the toxin. Bacteriocins differ from other peptide antibiotics in that their synthesis depends on de novo protein synthesis.

Various bacteriocins produced by bacteria. The bacteriocins produced by strains of E. coli are called colicins, those produced by B.megaterium as megacins etc. The genetic determinants responsible for the synthesis of different bacteriocins have been found to be on plasmids. So far, these have not been found integrated into the bacterial chromosome. In E. coli, these plasmids are called as colicinogenic factors (cot-factors) and a number of different types have been identified.

The principal ones that have been studied are col B. EI, E2, I and V. It has also been found that some col-factors such as B, I and V carry fertility determinants and therefore allow conjugation and plasmid transfer. Col B factors have also been found to control the synthesis of the sex pili. Some colfactors which cannot be transmitted have the ability to recombine with other col plasmids such as col EI and col E2.

These can then be transmitted provided the cell harbours a transmissible plasmid which may be defective only in one or more gene functions required for conjugation. Interestingly, col El and col E2 are mobilized not only by the transmissible col-factors but also by the F-factor.

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