DNA repair in Bacillus subtilis: excision repair capacity of competent cells.

Competent Bacillus subtilis were investigated for their ability to support the repair of UV-irradiated bacteriophage and bacteriophage DNA. UV-irradiated bacteriophage DNA cannot be repaired to the same level as UV-irradiated bacteriophage, suggesting a deficiency in the ability of competent cells to repair UV damage. However, competent cells were as repair proficient as noncompetent cells in their ability to repair irradiated bacteriophage in marker rescue experiments. The increased sensitivity of irradiated DNA is shown to be due to the inability of excision repair to function on transfecting DNA in competent bacteria. Furthermore, competent cells show no evidence of possessing an inducible BsuR restriction system to complement their inducible BsuR modification enzyme.