FIG. 2.

Microbial chemotaxis transducers. Metabolism-independent chemotaxis is governed by transmembrane receptors that have a periplasmic ligand-binding domain (shown in white). Energy taxis is governed by all membrane-associated receptors shown: either redox-responsive cofactors (FAD, heme) or charge-sensitive amino acid residues in a close proximity to the membrane might serve as the sensors (see the text for details). A specialized receptor binding oxygen directly is shown on the right. Hatched ovals represent conserved signaling modules. Cytoplasmic sensing domains are shown in black.