Competence in Bacillus subtilis Transformation System

Abstract

Changes in competence of B. subtilis 168 try- in relation to generation time and under other conditions were examined. When the generation time increased or decreased from that associated with maximum competence, compentence decreased. In a culture in balanced growth, competence remained at the same level for long periods. In supplemented medium, more bacteria became competent than in minimal medium. Aeration stimulated the development of competence which reached a higher peak than in an unaerated culture. When the medium was inoculated with spores, competence also developed. The smaller the inoculum of spores, the later the appearance of competence. Waves of competence often seen along the main curve of competence were influenced by the compositions of the media and by the inoculum size. During the growth cycle in a closed culture, the bacterial cells became competent and then lost this property. Competence was thus a transient state. The optical density of the bacterial suspension was a good guide to the development of competence but varied with the strains used and the culture conditions.