Recognition sites for chemotactic repellents of Bacillus subtilis

Repellents of B. subtilis include many membrane active compounds, such as uncouplers of oxidative phosphorylation, local anesthetics, chlorpromazine (a central nervous system depressant), and tetraphenylboron (a lipophilic anion). Normally, bacteria swim smoothly, and occasionally tumble, but addition of repellent causes all bacteria to tumble, then later resume original frequency of swimming and tumbling (adaptation). Bacteria adapted to repellent can then be tested to determine the minimum concentration (threshold) of the same or different repellents that causes tumbling. The results indicate that repellents act as (saturable) recognition sites, which differ for chemically different species. An implication is that uncouplers of oxidative phosphorylation affect cell properties by interaction at specific locations.