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CheB is required for behavioural responses to negative stimuli during chemotaxis in Bacillus subtilis
Author(s) -
Kirby John R.,
Niewold Timothy B.,
Maloy Stanley,
Ordal George W.
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01676.x
Subject(s) - chemotaxis , asparagine , demethylation , biology , bacillus subtilis , receptor , mutant , biochemistry , methylation , wild type , microbiology and biotechnology , amino acid , genetics , dna methylation , dna , gene expression , gene , bacteria
The methyl‐accepting chemotaxis protein, McpB, is the sole receptor mediating asparagine chemotaxis in Bacillus subtilis . In this study, we show that wild‐type B. subtilis cells contain ≈ 2000 copies of McpB per cell, that these receptors are localized polarly, and that titration of only a few receptors is sufficient to generate a detectable behavioural response. In contrast to the wild type, a cheB mutant was incapable of tumbling in response to decreasing concentrations of asparagine, but the cheB mutant was able to accumulate to low concentrations of asparagine in the capillary assay, as observed previously in response to azetidine‐2‐carboxylate. Furthermore, net demethylation of McpB is logarithmically dependent on asparagine concentration, with half‐maximal demethylation of McpB occurring when only 3% of the receptors are titrated. Because the corresponding methanol production is exponentially dependent on attractant concentration, net methylation changes and increased turnover of methyl groups must occur on McpB at high concentrations of asparagine. Together, the data support the hypothesis that methylation changes occur on asparagine‐bound McpB to enhance the dynamic range of the receptor complex and to enable the cell to respond to a negative stimulus, such as removal of asparagine.