Sensory adaptation and deadaptation by Bacillus subtilis.

Cells of Bacillus subtilis, when tethered by using antiflagellar antibody, rotate briefly counterclockwise (swimming behavior) or clockwise (tumbling behavior) when amino acids are added or removed, respectively. "Dissociation constants" for attractant-binding site interactions, calculated from duration of the rotational response to addition of amino acids, agreed with those calculated for their removal and with previous values calculated from sensitivity capillary assays. The ratio of adaptation times for addition versus removal of attractant averaged 1.7, which differs greatly from the value of 50 for Escherichia coli.