Cloning and characterization of genes encoding methyl-accepting chemotaxis proteins in Bacillus subtilis

Several genes homologous to the methyl-accepting chemotaxis proteins (MCPs) of Escherichia coli have been cloned and characterized from the Gram-positive bacterium, Bacillus subtilis. Sequence analysis reveals four large open reading frames, designated mcpA, mcpB, tlpA, and tlpB, each encoding a predicted 72-kDa protein. These proteins exhibit strong homology to chemoreceptors from several organisms, although similarity is limited to the C-terminal domain. These transducer genes were mapped to a chromosomal position of 279 degrees, which is distant from previously identified fla, mot, or che loci. Each gene was inactivated by insertion of a nonpolar chloramphenicol acetyltransferase cassette in the N-terminal region. In vivo methylation of the bacterial strain deficient in mcpA revealed the loss of several methylated bands in the range of the MCP previously designated as H1, and greatly reduced methylation of the MCP designated as H2. Furthermore, this bacterial strain exhibited a chemotaxis deficiency toward glucose and alpha-methyl-glucoside. Inactivation of mcpB caused a reduction in methylation of the MCP designated as H3, while chemotaxis toward asparagine, aspartate, glutamine, and histidine was significantly impaired in this strain. Despite strong homology, inactivation of tlpA and tlpB did not result in an observed deficiency in chemotaxis. Most unusually, these mutant strains exhibited a striking tendency to adhere together and resisted disaggregation.