A small gene, designated comS, located within the coding region of the fourth amino acid‐activation domain of srfA, is required for competence development in Bacillus subtilis

The valine‐activation domain‐encoding portion of the srfA locus srfA‐d4 is not only involved in the non‐ribosomal synthesis of surfactin, but is also required for the regulation of competence development. In this study we show that impairment of the adenylation activity of the valine‐activating domain did not affect competence development. Deletion analysis and complementation studies delineated the competence‐required portion of srfA‐d4 to a 168bp fragment, which contains a small open reading frame (ORF), designated comS, encoding a polypeptide of 46 amino acids, embedded within, but translated in, a frame different from that of srfA‐d4. Introduction of an amber mutation in the comS‐coding frame prevented competence development, demonstrating the involvement of comS in this prokaryotic specialization process.