SEQUENCE AND PROPERTIES OF MECA, A NEGATIVE REGULATOR OF GENETIC COMPETENCE IN BACILLUS-SUBTILIS

The development of competence in Bacillus subtilis is regulated by gro wth conditions and several regulatory genes. In complex media competen ce development is poor, and there is little or no expression of late c ompetence genes. mec mutations permit competence development and late competence gene expression in complex media, and bypass the requiremen ts for many of the competence regulatory genes. In this paper we descr ibe the cloning and characterization of mecA. The mecA gene product ac ts negatively in the development of competence. Null mutations in mecA allowed expression of a late competence gene comG, under conditions w here it is not normally expressed, including in complex media and in c ells mutant for several competence regulatory genes. Overexpression of MecA from a multicopy plasmid resulted in inhibition of comG transcri ption. The DNA sequence of mecA was determined and the predicted gene product showed no significant similarity to any protein in the databas e. Expression of a mecA-lacZ translational fusion was constitutive dur ing growth and did not vary significantly in the different media teste d. The role of mecA in competence development and other stationary pha se phenomena is discussed.