ROLE OF METHYLATION IN AEROTAXIS IN BACILLUS-SUBTILIS

Taxis to oxygen (aerotaxis) in Bacillus subtilis was characterized in a capillary assay and in a temporal assay in which the concentration o f oxygen in a flow chamber was changed abruptly. A strong aerophilic r esponse was present, but there was no aerophobic response to high conc entrations of oxygen. Adaptation to a step increase in oxygen concentr ation was impaired when B. subtilis cells were depleted of methionine to prevent methylation of the methyl-accepting chemotaxis proteins. Th ere was a transient increase in methanol release when wildtype B. subt ilis, but not a cheR mutant that was deficient in methyltransferase ac tivity, was stimulated by a step increase or a step decrease in oxygen concentration. The methanol released was quantitatively correlated wi th demethylation of methyl-accepting chemotaxis proteins. This indicat ed that methylation is involved in aerotaxis in B. subtilis in contras t to aerotaxis in Escherichia coli and Salmonella typhimurium, which i s methylation independent.