DegU and Spo0A Jointly Control Transcription of Two Loci Required for Complex Colony Development byBacillus subtilis

Abstract

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 DegUϳphosphate, but transcription is inhibited by direct AbrB binding to the promoter regions. Inhibition of transcription by AbrB is relieved when Spo0Aϳphosphate 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.

Division of Labor in Biofilms: the Ecology of Cell Differentiation

“…TasA assembles into amyloid-like fibers that attach to cell walls via an accessory protein, TapA (111,112). Another protein that contributes to the extracellular matrix is BslA, which is important for surface hydrophobicity (113)(114)(115)(116). However, unlike the epsA-O and tapA operons, bslA expression occurs in all of the cells within the population (116).…”

SwrAA activates poly-γ-glutamate synthesis in addition to swarming in Bacillus subtilis

“…Activation of DegU and of a second transcriptional regulator such as Spo0A has been recently found to be required for the expression of aprE, yvcA and yvaB in B. subtilis (Veening et al, 2008a;Verhamme et al, 2009) and such a dual regulation has been described as a logic AND gate (Veening et al, 2008b). Although it would be tempting to add the pgs operon to the list of genes regulated by AND gate systems, the lack of phenotypes produced by SwrAA alone (in the absence of DegU~P) rules out the existence of two independent regulators, as required by this logic circuitry.…”

A pivotal role for the response regulator DegU in controlling multicellular behaviour

“…Second, the levels of DegU~P in the cell must be high. This dual requirement of DegU and Spo0A activation as part of a genetic logic-AND network might represent a common mechanism for co-ordinating entry into the different multicellular behavioural processes of B. subtilis (Veening et al, 2008a, b;Verhamme et al, 2008). It remains to be seen whether intracellular fluctuations of phosphorylated DegU and Spo0A combined with intrinsic differences in promoter binding affinities coordinate the different multicellular behavioural processes manifested by B. subtilis.…”

“…YvcA is a putative membrane-bound lipoprotein required for complex colony development in NCIB 3610 but not for pellicle formation in ATCC 6051 (Kobayashi, 2007;Verhamme et al, 2007). A complex genetic circuit that is dependent on activation of DegU and Spo0A ensuring yvcA and yuaB transcription during complex colony development in B. subtilis NCIB 3610 has recently been described (Verhamme et al, 2008).…”

“…The other two targets for DegU are the proteins, YuaB and YvcA. YuaB is a small secreted protein required for pellicle formation and complex colony development in ATCC 6051 and NCIB 3610 (Kobayashi, 2007;Verhamme et al, 2008). YvcA is a putative membrane-bound lipoprotein required for complex colony development in NCIB 3610 but not for pellicle formation in ATCC 6051 (Kobayashi, 2007;Verhamme et al, 2007).…”