Chemotactic repellents of Bacillus subtilis

A number of membrane-active agents, including uncouplers of oxidative phosphorylation, a permeant anion, and local anaesthetics, are repellents of Bacillus subtilis. These bacteria normally swim, but tumble occasionally. However, when given such a reagent, they tumble and then later resume the original frequency of swimming and tumbling (i.e they adapt). We suggest that repellents of B. subtilis act directly on the membrane to cause tumbling, rather than through orthodox chemoreceptors as for enteric bacteria, and further, that decrease of ≈, the high energy state of the membrane interpreted as electrochemical gradient of H⁺ ions across the membrane (chemiosmotic hypothesis), causes tumbling and increase causes swimming.