Intercellular Effects on Development of Competence in Bacillus subtilis

Abstract

The intercellular transfer of competence during growth under the conditions specified by the transformation procedure of Spizizen was investigated with Bacillus subtilis 168. The rate of competence development as assayed uniformly in medium B was not affected by variations in the cell concentration, although the first appearance of transformants occurred earlier with high cell densities in medium A, approximately in proportion to the onset of the stationary phase in the culture. Growth in the presence of Pronase enhanced the frequency of transformation, but did not detectably alter the kinetics of competence development. The rate of competence increase in physiologically noncompetent cultures was not changed by mixing with competent cultures either in medium A or in medium B; however, an early appearance of transformants was noted in mixed cultures in which the proportion of competent to noncompetent cells prevented exponential growth of the noncompetent strain. These experiments indicate that the normal development of competence in B. subtilis is not mediated by a soluble or loosely bound protein factor capable of transmitting competence directly via cell contact. The onset of competence is thus a function of internal physiological changes which are induced by the overall metabolic state of the culture.