The bacterium Escherichia coli exhibits chemotactic behavior at temperatures ranging from approximately 20 °C to at least 42 °C. This behavior is controlled by clusters of transmembrane chemoreceptors made from trimers of dimers that are linked together by cross-binding to cytoplasmic components. By detecting fluorescence energy transfer between various components of this system, we studied the underlying molecular behavior of these receptors in vivo and throughout their operating temperature range. We reveal a sharp modulation in the conformation of unclustered and clustered receptor trimers and, consequently, in kinase activity output. These modulations occurred at a characteristic temperature that depended on clustering and were lower for receptors at lower adaptational states. However, in the presence of dynamic adaptation, the response of kinase activity to a stimulus was sustained up to 45 °C, but sensitivity notably decreased. Thus, this molecular system exhibits a clear thermal sensitivity that emerges at the level of receptor trimers, but both receptor clustering and adaptation support the overall robust operation of the system at elevated temperatures.
Bibliographical noteFunding Information:
We gratefully thank Sandy Parkinson for providing strains, engaging in discussions, and offering helpful comments on this manuscript. We also thank Victor Sourjik for strains and many helpful discussions. This work was supported by the Israeli Foundation of Sciences and Humanities .
- bacterial chemotaxis
- fluorescence polarization
- receptor clustering
- thermal sensitivity