MOLECULAR-CLONING AND SEQUENCE OF COMK, A GENE REQUIRED FOR GENETIC COMPETENCE IN BACILLUS-SUBTILIS

The transformation-deficient strain E26, isolated as a pHV60 insertion mutant, was used to isolate comK, a novel transcription unit required for genetic competence in Bacillus subtilis. Mutational analysis and sequence determination showed that comK contained one open reading fra me (ORF), which could encode a protein of 192 amino acid residues with a predicted molecular weight of 22 500. An integrated copy of comK no t only complemented the competence deficiency of a comK deletion mutan t, but also that of strains E26 and FB93. Expression of comK occurred exclusively in glucose-based minimal medium during the transition to s tationary growth phase. Furthermore, the expression of late competence genes appeared to be dependent on the gene product of comK, the expre ssion of which in turn depended on the presence of a functional comL ( or srfA) transcription unit. These epistatic interactions indicate tha t comK is a competence locus occupying an intermediate position in the competence signal transduction network. Primer extension analysis sho wed that comK has one major transcription start site, preceded by a se quence resembling the consensus promoter used by the sigma(A) form of RNA polymerase.