Part of a major quorum-sensing system that regulates the development of genetic competence (PubMed:1715859, PubMed:11751817). Involved in the maturation of the competence pheromone ComX (PubMed:11751817, PubMed:31670609). Acts by catalyzing the transfer of a farnesyl group on the ComX pheromone (PubMed:31670609). Shows weak geranylation activity with geranyl diphosphate (GPP) (PubMed:31670609). (2E,6E)-farnesyl diphosphate + L-tryptophyl-[protein] = (2S,3R)-3-farnesyl-2,3-dihydro-2,N(alpha)-cyclo-L-tryptophyl-[protein] + diphosphate Binds 2 Mg(2+) ions per subunit. Expression is maximal early in growth and declines as the cells approach the stationary phase. Disruption of the gene prevents the development of competence as well as the transcription of comG, a late competence operon (PubMed:1715859). Disruption also decreases the expression of srfA, a regulatory operon needed for the expression of competence (PubMed:1715859). The DNA sequences encoding comQ, comX and the N-terminal two-thirds of comP show a striking polymorphism, which determines the specificity of the quorum-sensing system in the different pherotypes of Bacillus. Belongs to the FPP/GGPP synthase family.