Amino acid chemotaxis in Bacillus subtilis

In Bacillus subtilis and in other bacteria chemotaxis receptors act as sensors for the presence of specific compounds in the surrounding environment. Cells can either be attracted or repelled by these compounds. If they are attracted they start to swim toward higher concentrations and away from high concentrations if they are repelled. We have demonstrated that a gene (mcpC), originally recognized as purine regulated, encodes a third methyl-accepting chemotaxis receptor protein. Two receptors have previously been found in B. subtilis. McpA is involved in taxis to a-glucosides and McpB is responsible for taxis to the amino acid asparagine. The novel sensor McpC is essential for taxis to several amino acids and we therefor conclude that this protein is the general amino acid sensor in Bacillus subtilis.The transcription start site of the mcpC gene was determined and we found a consensus sigma-D- requiring promoter sequence upstream of the start site. We also demonstrated that mcpC was not expressed in a sigD genetic background.