(53c) Spatial Dynamics In Bacterial Signal Transduction

Chemotaxis is the process by which cells sense chemical gradients in their environment and then move towards more favorable conditions. In bacteria, the chemotaxis pathways all appear utilize a modified two-component system to sense and respond to chemicals, where the receptors form ternary complexes with the CheA histidine kinase and the CheW adaptor protein. The clustering of these ternary complexes into semi-ordered hexagonal lattices has been documented in multiple organisms and is presumably conserved in all species of chemotactic bacteria. These arrays are thought to amplify the response to attractant binding.

Previously, these signally clusters were thought to be predominantly clustered at the cell poles. They were also thought to be static and reorganize only locally in response to attractant binding. However, recent studies have shown that these structures may in fact be much more fluid. In this study, we investigated the localization of the chemotaxis signaling complexes in the bacterium Bacillus subtilis using immunofluorescence and live-cell fluorescence. We found that the localization and composition of these signaling clusters change upon exposure to attractant. Moreover, these changes in clustering and localization are reversible with the prestimulus distribution reestablished in adapted cells. Finally, we also found that these changes are phosphorylation dependent.

These results collectively demonstrate that bacteria employ spatiotemporal mechanisms in signal transduction, something previously thought to occur only in eukaryotes. While we still do not fully understand the physiological significance of these changes, these result nonetheless demonstrate that signal transduction in bacteria is far more complex than initially envisioned with many new complexities still to be resolved.

References:

Wu K, Walukiewicz HE, Glekas GD, Ordal GW, Rao CV. Attractant binding induces distinct structural changes to the polar and lateral signaling clusters in Bacillus subtilis chemotaxis. Journal of Biological Chemistry, 286(4):2587-95, 2011.