Natural genetic competence in Bacillus subtilis is controlled by quorum-sensing (QS). The ComP- ComA two-component system detects the signalling molecule ComX, and this signal is transduced by a conserved phosphotransfer mechanism. ComX is synthesised as an inactive precursor and is then cleaved and modified by ComQ before export to the extracellular environment [1]. This family includes ComX phermones involved in quorum sensing. Amino acid sequence alignments between the two ComX precursor proteins in B. licheniformis, showed that their conservation is only restricted to the N-terminal ends. Moreover, high diversity in the amino acid sequence in C-terminus marked the pheromone-forming region, where, interestingly, the tryptophan residue is located [2].

1: Specific activation of the Bacillus quorum-sensing systems by isoprenylated pheromone variants. Ansaldi M, Marolt D, Stebe T, Mandic-Mulec I, Dubnau D; Mol Microbiol 2002;44:1561-1573. PMID:12067344

2: Genomic and molecular characterization of a novel quorum sensing molecule in Bacillus licheniformis. Esmaeilishirazifard E, De Vizio D, Moschos SA, Keshavarz T; AMB Express. 2017;7:78. PMID:28391484