Effect of receptor cooperativity on methylation dynamics in bacterial chemotaxis with weak and strong gradient

TL;DR

This study investigates how receptor cooperativity and gradient strength influence methylation dynamics in E. coli chemotaxis, revealing complex temporal behaviors dependent on cluster size and environmental conditions.

Contribution

It provides a detailed numerical analysis of methylation dynamics considering receptor cluster size and gradient strength, highlighting their combined effects on bacterial chemotactic response.

Findings

Methylation dynamics depend on receptor cluster size and gradient strength.

Short-term methylation is dominated by high receptor activity and demethylation.

Long-term methylation behavior varies with gradient and cluster size, especially in downhill runs.

Abstract

We study methylation dynamics of the chemoreceptors as an {\sl E.coli} cell moves around in a spatially varying chemo-attractant environment. We consider attractant concentration with strong and weak spatial gradient. During the uphill and downhill motion of the cell along the gradient, we measure the temporal variation of average methylation level of the receptor clusters. Our numerical simulations show that the methylation dynamics depends sensitively on the size of the receptor clusters and also on the strength of the gradient. At short times after the beginning of a run, the methylation dynamics is mainly controlled by short runs which are generally associated with high receptor activity. This results in demethylation at short times. But for intermediate or large times, long runs play an important role and depending on receptor cooperativity or gradient strength, the qualitative variation of methylation can be completely different in this time regime. For weak gradient, both for uphill and downhill runs, after the initial demethylation, we find methylation level increases steadily with time for all cluster sizes. Similar qualitative behavior is observed for strong gradient during uphill runs as well. However, the methylation dynamics for downhill runs in strong gradient show highly non-trivial dependence on the receptor cluster size. We explain this behavior as a result of interplay between the sensing and adaptation modules of the signaling network.