GENETIC NETWORKS CONTROLLING THE INITIATION OF SPORULATION AND THE DEVELOPMENT OF GENETIC COMPETENCE IN BACILLUS SUBTILIS

Abstract

Interconnected regulatory networks control the initiation of sporulation and the development of genetic competence in Bacillus subtilis. These two developmental pathways have both common and distinct elements and employ similar regulatory strategies. Activation of the ComK transcription factor serves to integrate many of the physiological signals that control competence development, including cell density signals. The cell density signals for competence are mediated by two different peptide pheromones, the ComX pheromone, a 9 or 10 amino acid peptide with a modified tryptophan residue, and the competence stimulating factor, CSF, which is at least in part a peptide. Activation of the Spo0A transcription factor by phosphorylation serves as a developmental checkpoint and to integrate several physiological signals that control entry into the sporulation pathway. The physiological signals are generated by conditions of nutrient deprivation, high cell density, the Krebs cycle, DNA replication, DNA damage, and some aspect of the chromosome partitioning machinery. Both the ComK and Spo0A transcription factors are part of autogenous regulatory loops that control entry into competence or sporulation.