Source of energy for gliding motility in Flexibacter polymorphus: effects of metabolic and respiratory inhibitors on gliding movement

Abstract

The effects of selected metabolic and respiratory inhibitors on the gliding motility of Flexibacter polymorphus were examined. Motility and oxygen consumption were quantitatively inhibited in a reversible manner by specific respiratory poisons, suggesting that gliding velocity was linked to electron transport activity. Arsenate had little influence on the number or rate of gliding filaments, despite a 95% decrease in the concentration of intracellular adenosine 5'-triphosphate (ATP). At concentrations of cyanide or azide that abolished gliding movement, cells possessed a level of ATP that should have been sufficient to allow motility. Proton-conducting uncouplers of oxidative phosphorylation, such as carbonylcyanide m-chlorophenylhydrazone (CCCP) and tetrachlorosalicylanilide, strongly inhibited locomotion yet did not suppress respiratory activity or intracellular ATP sufficiently to account for their effect on movement. Inhibition of motility by CCCP (but not by tetrachlorosalicylanilide) was partially reversed by sulfhydryl compounds. However, unlike CCCP, inhibition of motility by p-chloromercuribenzoate, a known sulfhydryl-blocking reagent, was associated with a corresponding reduction in respiratory activity and ATP content of cells. Protein synthesis was not blocked by concentrations of CCCP inhibitory for motility, indicating that utilization of existing ATP in this energy-requiring process was not impaired. These data suggest (but do not unequivocally prove) that ATP may not function as the sole energy donor for the gliding mechanism, but that some additional product of electron transport is required (e.g., the intermediate of oxidative phosphorylation).