Effect of potassium phosphate on Bacillus subtilis competence mutants

We have previously described the isolation and characterization of four Bacillus subtilis competence-deficient mutants (J. Bacteriol. (1984) 157, 152–157). Further experiments, reported here, have shown that the transformation frequency of two of the mutants (FB92 and FB94) can be increased by the addition of high concentrations of potassium phosphate buffer present in the concentrated supernatant. This buffer stimulates up to 40–50 times the transformation frequency of FB92 and FB94 strains, while it has an inhibitory effect on the other two mutants and on the wild-type strain. Potassium phosphate inhibits DNA binding to competent cells but, at the same time, activates a second much less efficient binding system which partly restores the capacity of FB92 and FB94 mutants to take up DNA.