A common bacterial strategy for monitoring environmental challenges is to use two-component systems, which consist of a sensor histidine kinase (HK) and a response regulator (RR). In the food-borne pathogen Bacillus cereus, the alternative sigma factor sB is activated by the RR RsbY. Here we present strong indications that the PP2C-type phosphatase RsbY receives its input from the multi-sensor hybrid kinase BC1008 (renamed RsbK). Genome analyses revealed that, across bacilli, rsbY and rsbK are located in a conserved gene cluster. A B. cereus rsbK deletion strain was shown to be incapable of inducing sB upon stress conditions and was impaired in its heat adaptive response. Comparison of the wild-type and rsbK mutant transcriptomes upon heat shock revealed that RsbK was primarily involved in the activation of the sB-mediated stress response. Truncation of the RsbK RR receiver domain demonstrated the importance of this domain for sB induction upon stress. The domain architecture of RsbK suggests that in the B. cereus group and in other bacilli, environmental and intracellular stress signalling routes are combined into one single protein. This strategy is markedly different from the sB activation pathway in other low-GC Gram-positives.
- gram-positive bacteria
- 2-component signal-transduction
- multiple sequence alignment
- tumefaciens vira protein
- energy stress
A novel hybrid kinase is essential for regulating the σB-mediated stress response of Bacillus cereus.