IDENTIFICATION OF COMS, A GENE OF THE SRFA OPERON THAT REGULATES THE ESTABLISHMENT OF GENETIC COMPETENCE IN BACILLUS-SUBTILIS

Genetic competence (the ability to internalize exogenous DNA) in Bacil lus subtilis is dependent on a regulatory pathway that activates the e xpression of a battery of competence-specific genes. The srfA operon, encoding the subunits of surfactin synthetase, which catalyzes the non ribosomal synthesis of the peptide antibiotic surfactin, also function s in the competence regulatory pathway. The DNA encoding only one of t he seven amino acid-activating domains of surfactin synthetase, the va line-activating domain (srfAB1), is necessary for competence. Deletion analysis revealed that a 569-bp fragment of srfAB1, fused to the srfA promoter, complements a srfA deletion mutation (Delta srfA) with resp ect to competence. This fragment contains an open reading frame consis ting of 46 amino acids (orf46), which is out of frame with srfAB1. A f rameshift mutation in srfAB upstream of orf46 has no effect on compete nce but a frameshift and nonsense mutation in orf46 resulted in failur e to complement the Delta srfA mutation. These results indicate that o rf46 encodes the srfA-associated competence regulatory factor. Compute r-aided analysis of the putative orf46 product (ComS) shows similarity to the homeodomain of the POU domain class of eukaryotic transcriptio nal regulators.