Regulation and production of extracellular signaling molecules in Bacillus subtilis

Abstract

Many bacteria use chemical signals for intercellular communication. These signals accumulate extracellularly and are sensed at threshold concentrations to alter gene expression. Bacillus subtilis uses cell-cell signals to control genetic competence, sporulation, degradative enzyme production and antibiotic synthesis. A family of peptide signals controls gene expression in B. subtilis by regulating transcription factors. I showed that the transcription of these peptide regulators is in turn controlled in part by the alternate sigma factor sigma-H. The activity of sigma-H is stimulated by nutrient starvation I determined that B. subtilis produces a putative interspecies signaling activity, AI-2, that depends on the conserved protein LuxS. To determine the effect of luxS on regulation of transcription in B. subtilis, I performed experiments to compare the transcriptional profiles of B. subtilis when luxS was deleted or overexpressed. I found no significant change in transcriptional profiles, indicating that B. subtilis does not use luxS/AI-2 for signaling under these conditions.