Involvement of many chemotaxis sensors in negative chemotaxis to ethanol in Ps29.

Ps29 showed repellent responses to alcohols including methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1,3-propanediol and prenol. Ps29 possesses 22 putative chemoreceptors known as methyl-accepting chemotaxis proteins (MCPs). To identify a MCP involved in negative chemotaxis to ethanol, we measured ethanol chemotaxis of a complete collection of single gene deletion mutants of Ps29. However, all the mutants showed repellent responses to ethanol comparable to that of the wild-type strain. We constructed a stepwise- and multiple- gene deletion mutant collection of Ps29. Analysis of the collection found that an 18--knockout mutant (strain POC18) failed to respond to ethanol. Complementation analysis using POC18 as the host strain found that introduction of , , , , and restored the ability of POC18 to respond to ethanol. However, unexpectedly, strain POC10II, harbouring unmarked deletions in 10 genes including , , , , and showed repellent responses to ethanol comparable to that of wild-type Ps29. We hypothesised that multiple mutations in POC18 led to a shortage of MCPs required for formation of functional chemoreceptor arrays. When pPS16 (encoding McpP involved in phosphate chemotaxis) was introduced into POC18, POC18(pPS16) did not respond to phosphate. This result supports the hypothesis. But, genetic analysis revealed that MCPs (Mcp07, Mcp13, Mcp20 and Mcp21) are not essential for ethanol chemotaxis. Thus, we conclude that many and unspecified MCPs are involved in negative chemotaxis to ethanol in Ps29.