Transformation in Bacillus subtilis: different affinities for DNA-binding to competent cells and to membrane vesicles

Abstract

Comparison between dose-response curves to homologous and to T*4 (non-glucosylated) DNA in cells and in membrane vesicles, isolated from competent Bacillus subtilis, indicated the presence of two kinds of DNA receptors in the membrane vesicles system. This was confirmed by competition experiments. In addition, concentration dependence for binding of low-molecular weight homologous DNA also revealed the existence of more than one DNA receptor site in competent cells of B. subtilis. However, no differences in the uptake of sheared or intact DNA was observed, which indicates that only one kind of receptors is involved in the entry of donor DNA. Competition experiments in binding, uptake, and transformation, with the possible combinations of sheared or intact DNAs, suggested that the former has more affinity for the binding sites than the latter. This finding is also supported by the results obtained in membrane vesicles, either in competition or in chasing experiments.