Spatial Regulation of Histidine Kinases Governing Biofilm Formation inBacillus subtilis

Abstract

Bacillus subtilis is able to form architecturally complex biofilms on solid medium due to the production of an extracellular matrix. A master regulator that controls the expression of the genes involved in matrix synthesis is Spo0A, which is activated by phosphorylation via a phosphorelay involving multiple histidine kinases. Here we report that four kinases, KinA, KinB, KinC, and KinD, help govern biofilm formation but that their contributions are partially masked by redundancy. We show that the kinases fall into two categories and that the members of each pair (one pair comprising KinA and KinB and the other comprising KinC and KinD) are partially redundant with each other. We also show that the kinases are spatially regulated: KinA and KinB are active principally in the older, inner regions of the colony, and KinC and KinD function chiefly in the younger, outer regions. These conclusions are based on the morphology of kinase mutants, real-time measurements of gene expression using luciferase as a reporter, and confocal microscopy using a fluorescent protein as a reporter. Our findings suggest that multiple signals from the older and younger regions of the colony are integrated by the kinases to determine the overall architecture of the biofilm community.

In vivo functional characterization of the transmembrane histidine kinase KinC in Bacillus subtilis

“…Second, using the undomesticated strain, we confirmed that the biofilm formation is dependent on phosphorelay (Fig. 2a, b) as reported by McLoon et al (2011). For quantitative assay of biofilm formation, we measured expression levels of the PtapA-lacZ construct in MSgg medium and found that the reporter activities were significantly lower in the spo0F, spo0B or spo0A mutants than those in the WT strain (Fig.…”

Connection of KinC to flotillins and potassium leakage in Bacillus subtilis

“…The kinC mutant phenotype (Fig. 2a, b) appears strikingly different to what has been published by several groups (Ló pez et al, 2009a;McLoon et al, 2011). Furthermore, we have never detected early sporulation in a kinC mutant.…”

Insight into the sporulation phosphorelay: Crystal structure of the sensor domain of Bacillus subtilis histidine kinase, KinD

“…KinA contains three cytosolic PerArnt-Sim (PAS) domains that apparently sense starvation signals, but the identity of this signal is unknown. 12 In contrast, KinC and KinD appear to have a role in initiating the transition from exponential growth to stationary phase by generating low levels of Spo0A$ P. 6,13 KinC is activated in response to potassium membrane leakage and this activation depends on a single cytosolic PAS sensory domain. 14 KinD has been shown to delay the onset of sporulation 15 and has been proposed to act as a phosphatase under certain conditions, which regulates the level of Spo0A$ P. Its signal has been unidentified as of yet.…”