Fig. 1.

Mechanism involved in flagella-driven chemotaxis in Gram-negative bacteria. In the presence of chemoattractants, the flagellum preferably switches to counter-clockwise rotation, propelling the cell towards the chemoattractants. When chemoattractant concentrations is low, or when chemorepellents are detected by MCP, CheA is autophosphorylated and phosphorylates CheY and CheB. CheY induces in turn a flagellar rotation change through the switch complex component FliM, leading to clockwise rotation and random cell movements. Regulation of this mechanism is mediated by CheR, CheB, and CheZ, respectively through methylation, demethylation and dephosphorylation. MCP: Methyl-accepting chemotaxis proteins.