Dataset Information

A combination of glycerol and manganese promotes biofilm formation in Bacillus subtilis via histidine kinase KinD signaling.

ABSTRACT: The spore-forming bacterium Bacillus subtilis forms matrix-enclosed biofilms in response to environmental cues that to date remain poorly defined. Biofilm formation depends on the synthesis of an extracellular matrix, which is indirectly regulated by the transcriptional regulator Spo0A. The activity of Spo0A depends on its phosphorylation state. The level of phosphorylated Spo0A (Spo0A~P) is controlled by a network of kinases and phosphatases, which respond to environmental and physiological signals. In spite of significant progress in understanding biofilm development, the fundamental question of how cells sense the environmental cues that trigger biofilm formation has largely remained unaddressed. Here, we report that biofilm formation of B. subtilis in LB medium is triggered by a combination of glycerol and manganese (GM). Moreover, LB medium with GM significantly stimulates biofilm-associated sporulation and production of an undefined brown pigment. We further show that transcription of the major operons responsible for matrix production and biofilm formation is dramatically enhanced in response to GM. We also establish that KinD is a principal histidine kinase responsible for sensing the presence of GM exclusively by its extracellular CACHE domain. Finally, we show that GM has a similar biofilm-promoting effect in two related Bacillus species, B. licheniformis and B. cereus, indicating that the biofilm-promoting effect of GM is conserved in Bacillus species.

SUBMITTER: Shemesh M

PROVIDER: S-EPMC3697245 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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A combination of glycerol and manganese promotes biofilm formation in Bacillus subtilis via histidine kinase KinD signaling.

Shemesh Moshe M Chai Yunrong Y

Journal of bacteriology 20130405 12

The spore-forming bacterium Bacillus subtilis forms matrix-enclosed biofilms in response to environmental cues that to date remain poorly defined. Biofilm formation depends on the synthesis of an extracellular matrix, which is indirectly regulated by the transcriptional regulator Spo0A. The activity of Spo0A depends on its phosphorylation state. The level of phosphorylated Spo0A (Spo0A~P) is controlled by a network of kinases and phosphatases, which respond to environmental and physiological sig ...[more]

PMID: 23564171

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Project description:In Bacillus subtilis, biofilm and sporulation pathways are both controlled by a master regulator, Spo0A, which is activated by phosphorylation via a phosphorelay-a cascade of phosphotransfer reactions commencing with autophosphorylation of histidine kinases KinA, KinB, KinC, KinD, and KinE. However, it is unclear how the kinases, despite acting via the same regulator, Spo0A, differentially regulate downstream pathways, i.e., how KinA mainly activates sporulation genes and KinC mainly activates biofilm genes. In this work, we found that KinC also downregulates sporulation genes, suggesting that KinC has a negative effect on Spo0A activity. To explain this effect, with a mathematical model of the phosphorelay, we revealed that unlike KinA, which always activates Spo0A, KinC has distinct effects on Spo0A at different growth stages: during fast growth, KinC acts as a phosphate source and activates Spo0A, whereas during slow growth, KinC becomes a phosphate sink and contributes to decreasing Spo0A activity. However, under these conditions, KinC can still increase the population-mean biofilm matrix production activity. In a population, individual cells grow at different rates, and KinC would increase the Spo0A activity in the fast-growing cells but reduce the Spo0A activity in the slow-growing cells. This mechanism reduces single-cell heterogeneity of Spo0A activity, thereby increasing the fraction of cells that activate biofilm matrix production. Thus, KinC activates biofilm formation by controlling the fraction of cells activating biofilm gene expression. IMPORTANCE In many bacterial and eukaryotic systems, multiple cell fate decisions are activated by a single master regulator. Typically, the activities of the regulators are controlled posttranslationally in response to different environmental stimuli. The mechanisms underlying the ability of these regulators to control multiple outcomes are not understood in many systems. By investigating the regulation of Bacillus subtilis master regulator Spo0A, we show that sensor kinases can use a novel mechanism to control cell fate decisions. By acting as a phosphate source or sink, kinases can interact with one another and provide accurate regulation of the phosphorylation level. Moreover, this mechanism affects the cell-to-cell heterogeneity of the transcription factor activity and eventually determines the fraction of different cell types in the population. These results demonstrate the importance of intercellular heterogeneity for understanding the effects of genetic perturbations on cell fate decisions. Such effects can be applicable to a wide range of cellular systems.

Project description:Bacillus subtilis forms robust biofilms in the presence of large amounts of carbon sources, such as glycerol. However, little is known about the importance of the metabolic systems, or the relationship between metabolic systems and regulatory systems, involved in biofilm formation. Glutamate synthase, encoded by gltAB, is an enzyme that converts 2-ketoglutarate (a tricarboxylic acid [TCA] cycle intermediate) and glutamine into glutamate, which is a general amino group donor in metabolism. Here, we show that a ?gltA mutant exhibited early arrest of biofilm formation in complex medium containing glycerol. This phenotype was not due to glutamate auxotrophy. Consistent with its biofilm formation phenotype, the ?gltA mutant exhibited an early decrease in expression of the epsA and tapA operons, which are responsible for production of biofilm matrix polymers. This resulted from decreased activity of their regulator, Spo0A, as evidenced by reduced expression of other Spo0A-regulated genes in the ?gltA mutant. The ?gltA mutation prevented biofilm formation only in the presence of large amounts of glycerol. Moreover, limited expression of citrate synthase (but not other TCA enzymes) restored biofilm-forming ability to the ?gltA mutant. These results indicate that the ?gltA mutant accumulates an inhibitory intermediate (citrate) in the TCA cycle in the presence of large amounts of glycerol. The ?gltA mutant formed biofilms when excess iron was added to the medium. Taken together, the data suggest that accumulation of citrate ions by the ?gltA mutant causes iron shortage due to chelation, which prevents activation of Spo0A and causes defective biofilm formation.IMPORTANCE Bacillus subtilis, a model organism for bacterial biofilm formation, forms robust biofilms in a medium-dependent manner. Although the regulatory network that controls biofilm formation has been well studied, the importance of the underlying metabolic systems remains to be elucidated. The present study demonstrates that a metabolic disorder in a well-conserved metabolic system causes accumulation of an inhibitory metabolic intermediate that prevents activation of the system that regulates biofilm formation. These findings increase our understanding of the coordination between cellular metabolic status and the regulatory networks governing biofilm formation.

Dataset Information

A combination of glycerol and manganese promotes biofilm formation in Bacillus subtilis via histidine kinase KinD signaling.

Publications

A combination of glycerol and manganese promotes biofilm formation in Bacillus subtilis via histidine kinase KinD signaling.

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