Characterization of the molecular mechanisms controlling negative chemotaxis to copper in Caulobacter crescentus

In order to maintain their fitness, bacteria must quickly adapt to
environmental changes. It has been shown in the laboratory that the 2
functionally distinct progenies issued from the Caulobacter crescentus
asymmetrical cell division exhibit distinct responses to a toxic Copper (Cu)
stress. Although the sessile stalked cell engages a Cu detoxification-efflux
system, its flagellated sibling favours the flight towards a more appropriate
environment within a few minutes.
The present research project aims at identifying the molecular mechanisms
driving the flagellated cell chemotactic response to Cu. The important Cu
accumulation observed in the flagellated cell turns out to be required for the
chemotactic response. We will first determine whether this Cu accumulation
occurs in the periplasm or in the cytoplasm. We will next try to obtain
chemotaxis defective mutants by deleting the 19 predicted C. crescentus
chemoreceptors (MCP). The lack of chemotactic response will be assessed
by the Live Chemotaxis Imaging assay previously developed in the
laboratory. If this strategy is not conclusive, we will proceed to the
generation and the screening of a transpositional mutant library. The MCP
mutants will then be selected based on the presence of conserved MCP
domains and characterized in terms of (i) subcellular localization and (ii)
function by identifying the domain(s) binding Cu directly or indirectly. Then,
we will focus on the involvement of the conserved Che proteins in the Cu
chemotactic response. Finally, we will focus on the possible development of
a Cu memory by comparing the chemotactic response of naive flagellated
cells and flagellated cells born in a Cu-rich environment.