UNIQUE REGULATION OF CARBOHYDRATE CHEMOTAXIS IN BACILLUS-SUBTILIS BY THE PHOSPHOENOLPYRUVATE-DEPENDENT PHOSPHOTRANSFERASE SYSTEM AND THE METHYL-ACCEPTING CHEMOTAXIS PROTEIN MCPC

The phosphoenolpyruvate-dependent phosphotransferase system (PTS) play s a major role in the ability of Escherichia coli to migrate toward PT S carbohydrates, The present study establishes that chemotaxis toward PTS substrates in Bacillus subtilis is mediated by the PTS as well as by a methyl-accepting chemotaxis protein (MCP), As for E. coli, a B. s ubtilis ptsH null mutant is severely deficient in chemotaxis toward mo st PTS carbohydrates, Tethering analysis revealed that this mutant doe s respond normally to the stepwise addition of a PTS substrate (positi ve stimulus) but fails to respond normally to the stepwise removal of such a substrate (negative stimulus). An mcpC null mutant showed no re sponse to the stepwise addition or removal of D-glucose or D-mannitol, both of which are PTS substrates. Therefore, in contrast to E. coli P TS carbohydrate chemotaxis, B, subtilis PTS carbohydrate chemotaxis is mediated by both MCPs and the PTS; the response to positive stimulus is primarily McpC mediated, while the duration or magnitude of the res ponse to negative PTS carbohydrate stimulus is greatly influenced by c omponents of the PTS and McpC, In the case of the PTS substrate D-gluc ose, the response to negative stimulus is also partially mediated by M cpA, Finally, we show that B, subtilis EnzymeI-P has the ability to in hibit B, subtilis CheA autophosphorylation in vitro. We hypothesize th at chemotaxis in the spatial gradient of the capillary assay may resul t from a combination of a transient increase in the intracellular conc entration of EnzymeI-P and a decrease in the concentration of carbohyd rate-associated McpC as the cell moves down the carbohydrate concentra tion gradient. Both events appear to contribute to inhibition of CheA activity that increases the tendency of the bacteria to tumble. In the case of D-glucose, a decrease in D-glucose-associated McpA may also c ontribute to the inhibition of CheA. This bias on the otherwise random walk allows net migration, or chemotaxis, to occur.