DegU and Spo0A jointly control transcription of two loci required for complex colony development by Bacillus subtilis

Biofilm formation is an example of a multicellular process which depends on cooperative behavior and differentiation within a bacterial population. Our findings indicate that there is a complex feedback loop that maintains the stoichiometry of the extracellular matrix and other proteins required for complex colony development by Bacillus subtilis. Analysis of the transcriptional regulation of two DegU-activated genes that are required for complex colony development by B. subtilis revealed additional involvement of global regulators that are central to controlling biofilm formation. Activation of transcription from both the yvcA and yuaB promoters requires DegU approximately phosphate, but transcription is inhibited by direct AbrB binding to the promoter regions. Inhibition of transcription by AbrB is relieved when Spo0A approximately phosphate is generated due to its known role in inhibiting abrB expression. Deletion of SinR, a key coordinator of motility and biofilm formation, enhanced transcription from both loci; however, no evidence of a direct interaction with SinR for either the yvcA or yuaB promoter regions was observed. The enhanced transcription in the sinR mutant background was subsequently demonstrated to be dependent on biosynthesis of the polysaccharide component that forms the major constituent of the B. subtilis biofilm matrix. Together, these findings indicate that a genetic network dependent on activation of both DegU and Spo0A controls complex colony development by B. subtilis.