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Phosphatases modulate the bistable sporulation gene expression pattern in Bacillus subtilis.
Summary Spore formation in the Gram-positive bacterium Bacillus subtilis is a last resort adaptive response to starvation. To initiate sporulation, the key regulator in this process, Spo0A, needs to be activated by the so-called phosphorelay. Within a sporulating culture of B. subtilis, some cells initiate this developmental program, while other cells do not. Therefore, initiation of sporulation appears to be a regulatory process with a bistable outcome. Using a single cell analytical approach, we show that the autostimulatory loop of spo0A is responsible for generating a bistable response resulting in phenotypic variation within the sporulating culture. It is demonstrated that the main function of RapA, a phosphorelay phosphatase, is to maintain the bistable sporulation gene expression. As rapA expression is quorum regulated, it follows that quorum sensing influences sporulation bistability. Deletion of spo0E, a phosphatase directly acting on Spo0A approximately P, resulted in abolishment of the bistable expression pattern. Artificial induction of a heterologous Rap phosphatase restored heterogeneity in a rapA or spo0E mutant. These results demonstrate that with external phosphatases, B. subtilis can use the phosphorelay as a tuner to modulate the bistable outcome of the sporulating culture. This shows that B. subtilis employs multiple pathways to maintain the bistable nature of a sporulating culture, stressing the physiological importance of this phenomenon.
Bacillus subtilis/cytology, Bacillus subtilis/enzymology, Bacterial Proteins/genetics, Bacterial Proteins/metabolism, Culture Media, Flow Cytometry, Gene Expression Regulation, Bacterial, Phosphoprotein Phosphatases/genetics, Phosphoprotein Phosphatases/metabolism, Phosphoric Monoester Hydrolases/genetics, Phosphoric Monoester Hydrolases/metabolism, Promoter Regions, Genetic, Spores, Bacterial/physiology, Transcription Factors/genetics, Transcription Factors/metabolism, Transcription, Genetic
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