A Signal Transduction Network inBacillus subtilisIncludes the DegS/DegU and ComP/ComA Two-Component Systems

Abstract

Soil bacteria such as Bacillus subtilis are subject to drastic variations of environmental conditions such as temperature, humidity, and nutrient source availability. At the onset of the stationary phase, faced with a depletion of essential nutrients, B. subtilis can adopt several responses, including synthesis of macromolecule-degrading enzymes, competence for genetic transformation, increased motility and chemotaxis, antibiotic production, and finally, sporulation. Regulation by the B. subtilis two-component systems presents several original features. Some of these original features are discussed, within the framework of the DegS/DegU and ComP/ComA signal transduction network. The chapter describes degradative enzyme synthesis. Sequence similarities with two-component systems suggest the conserved His-189 residue of the DegS protein kinase and Asp-56 residue of the DegU response regulator as likely candidates for the respective phosphorylation sites of the two proteins. The chapter discusses competence gene expression, and signal transduction network. Both the ComP/ComA and DegS/DegU two-component systems control the expression of late competence genes; however, they seem to act through two different branches in the competence regulatory pathway that intersect to allow expression of comK. An exciting area of future research will be to identify the types of signals involved in regulation by each of these two-component systems and by the other regulators such as MecB/MecA and the ComQ-ComX-Spo0K pathway, as well as determining how these regulators interact within the signal transduction network.