Diversity of ligands recognized by the major classes of chemoreceptor LBDs. The following ligands for which direct binding was observed are shown (along with references for the corresponding evidence): E. coli Tar (Ec-Tar) (63), Ec-Tsr (50), C. testosteroni MCP2901 (Ct-MCP2901) (203), Ct-MCP2983 (204), Ct-MCP2201 (40), P. aeruginosa CtpH (Pa-CtpH) (22, 141), P. putida McpS (Pp-McpS) (164), Pp-McpQ (167), H. pylori TlpB (Hp-TlpB) (97, 109), Pp-McpP (168), B. subtilis McpC (Bs-McpC) (89), Bs-McpB (9, 180), C. jejuni CcaA (Cj-CcaA) (116), Cj-CcmL (38, 179), Pa-PctA (138), Pa-PctB (138), Pp-McpA (163), V. cholerae Mlp37 (Vc-Mlp37) (44), Vc-Mlp24 (205), S. meliloti McpU (Sm-McpU) (206), Cj-Tlp11 (119), Pa-PctC (138), Pp-McpG (34), Sm-McpX (207), Pp-McpU (163), and Pp-McpH (162).