Adaptation methylation-independent

A common denominator for the methylation-dependent adaptation and the CheZ-dependent termination or adaptation is that both processes are triggered by changes in the phosphorylation level of CheY. It appears that the complete mechanism of adaptation, methylation-dependent and independent, is still not fully resolved. Methylation-independent adaptation was also demonstrated in B. subtilis, where it was found to be very effective [366]. 

The methylation of MCPs plays a central role in sensory adaptation, since if the methylation reaction is blocked then sensory adaptation is halted, A considerable body of additional evidence supports a link between methylation and adaptation. The kinetics of adaptation and MCP methylation appear similar the attractant-induced increase in methylation and heilf-time of the reaction eire directly proportional to the adaptation time, rates of adaptation and methylation are fast, whereas de-adaptation and demethylation are slow. Different stimuli presented simultaneously produce cumulative effects on both the methylation reaction and adaptation time. Maintenance of the adapted state and of attractant-induced methylation are both methionine-independent as is the process of deadaptation and demethylation. The mechanisms that link methylation to adaptation are not yet fully defined, but the methylation reaction appears to alter the parameter that regulates the sensitivity of the orgemism to external chemical stimuli. 

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