Ingham C J, Armitage J P
Department of Botany and Microbiology, University College London, London, United Kingdom.
J Bacteriol. 1987 Dec;169(12):5801-7. doi: 10.1128/jb.169.12.5801-5807.1987.
The chemotactic response to a range of chemicals was investigated in the photosynthetic bacterium Rhodobacter sphaeroides, an organism known to lack conventional methyl-accepting sensory transduction proteins. Strong attractants included monocarboxylic acids and monovalent cations. Results suggest that the chemotactic response required the uptake of the chemoeffector, but not its metabolism. If a chemoeffector could block the uptake of another attractant, it also inhibited chemotaxis to that attractant. Sodium benzoate was not an attractant but was a competitive inhibitor of the propionate uptake system. Binding in an active uptake system was therefore insufficient to cause a chemotactic response. At different concentrations, benzoate either blocked propionate chemotaxis or reduced the sensitivity of propionate chemotaxis, an effect consistent with its role as a competitive inhibitor of uptake. Bacteria only showed chemotaxis to ammonium when grown under ammonia-limited conditions, which derepressed the ammonium transport system. Both chemotaxis and uptake were sensitive to the proton ionophore carbonyl cyanide m-chlorophenylhydrazone, suggesting an involvement of the proton motive force in chemotaxis, at least at the level of transport. There was no evidence for internal pH as a sensory signal. These results suggest a requirement for the uptake of attractants in chemotactic sensing in R. sphaeroides.
在光合细菌球形红杆菌中研究了对一系列化学物质的趋化反应，该生物体已知缺乏传统的甲基接受型传感转导蛋白。强引诱剂包括一元羧酸和单价阳离子。结果表明，趋化反应需要摄取化学效应物，但不需要其代谢。如果一种化学效应物能够阻断另一种引诱剂的摄取，它也会抑制对该引诱剂的趋化作用。苯甲酸钠不是引诱剂，但却是丙酸盐摄取系统的竞争性抑制剂。因此，在活性摄取系统中的结合不足以引起趋化反应。在不同浓度下，苯甲酸盐要么阻断丙酸盐趋化作用，要么降低丙酸盐趋化作用的敏感性，这一效应与其作为摄取竞争性抑制剂的作用一致。细菌只有在氨限制条件下生长时才对铵表现出趋化作用，这会解除铵转运系统的阻遏。趋化作用和摄取都对质子离子载体羰基氰化物间氯苯腙敏感，这表明质子动力至少在转运水平上参与了趋化作用。没有证据表明内部pH作为传感信号。这些结果表明，球形红杆菌的趋化传感需要摄取引诱剂。
