title: Control of tumbling in bacterial chemotaxis by divalent cation.
abstract: Chemotaxis is migration of organisms to higher concentrations of attractant or lower concentrations of repellent. Understanding the switch than controls whether the flagella rotate counterclockwise for swimming or clockwise for tumbling (thrashing about without making much forward progress) is central to understanding chemotaxis of peritrichous bacteria, since chemotaxis results from selective suppression of tumbles. Depletion of divalent cation by chelating agents in the presence of A23187, an ionophore that conveys divalent cation across membrane, causes incessant tumbling in Bacillus subtilis. Small additions of MgCl2 prevent this tumbling. In this tumbling condition, the bacteria which normally swim extensively when given attractant, do not respond even to 10 mM alanine, a strong attractant. MnCl2, by contrast to others potentiated by the ionophore. Permanent cations, including tetraphenylarsonium ion and triphenylmethylphosphonium ion, cause permanent swimming, even in the presence of A23187 and chelating agents. We propose that divalent cation, probably Mg2+ ion, binds to the switch to cause swimming and that, in the absence of divalent cation at the switch, the bacterium tumbles.
mesh_terms: D000409:Alanine / Q000494:pharmacology; D001152:Arsenicals / Q000494:pharmacology; D001412:Bacillus subtilis / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects*; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology*; D008345:Manganese / Q000494:pharmacology*; D009861:Onium Compounds / Q000494:pharmacology; D009943:Organophosphorus Compounds / Q000494:pharmacology; D014320:Triphenylmethyl Compounds; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D001152:Arsenicals; D002614:Chelating Agents; D009861:Onium Compounds; D009943:Organophosphorus Compounds; D014320:Triphenylmethyl Compounds; D014475:Uncoupling Agents; C011561:triphenylmethylphosphonium; D000001:Calcimycin; D008345:Manganese; D004533:Egtazic Acid; D004492:Edetic Acid; D008274:Magnesium; D000409:Alanine; D002118:Calcium