| Abstract: | Evidence is presented that chemotaxis requires ATP or a closely related metabolite, in addition to its known requirements of ATP for synthesis of S-adenosylmethionine (AdoMet) and maintenance of the proton motive force. Previous studies demonstrated a loss of tumbling and chemotaxis, and depletion of ATP when hisF auxotrophs of Salmonella typhimurium are starved for histidine (Galloway, R. J., and Taylor, B. L. (1980) J. Bacteriol. 144, 1068-1075). In the present study, intracellular AdoMet], membrane potential, and ATP] were measured in a hisF mutant of S. typhimurium. Membrane potential, determined from partitioning of 3H]tetraphenylphosphonium ion between the inside and the outside of the cell, was about -150 mV at pH 7.6, and did not decrease in histidine starvation but was slightly increased. The concentration of AdoMet decreased from 0.4 mM to 0.3 mM during starvation but when cycloleucine, an inhibitor of AdoMet synthetase, was used to decrease AdoMet] by a similar amount in histidine-fed cells there was little change in tumbling frequency. Intracellular ATP] was reduced from 4.5 mM to less than 0.2 mM by histidine starvation. About 0.2 mM ATP was necessary for spontaneous tumbling. A similar ATP] was required for tumbling in arsenate-treated cells. Adenine at concentrations as low as 20 nM caused a transient increase in both tumbling frequency and ATP] in histidine-starved cells. Thus, out of three parameters tested, only the intracellular ATP] correlated with changes in tumbling frequency in the histidine-starved cells. |
