Constitutive uptake and degradation of fatty acids by Yersinia pestis

Yersinia pestis was found to utilize palmitic acid as a primary carbon and energy source. No inhibition of growth by palmitic acid was observed. Comparison of palmitic acid uptake by cells pregrown either with or without palmitic acid demonstrated that fatty acid uptake was constitutive. High basal levels of two enzymes of beta-oxidation, beta-hydroxyacyl-coenzyme A dehydrogenase and thiolase, and the two enzymes of the glyoxylate shunt, isocitrate lyase and malate synthase, were found in cells grown in defined medium with glucose. Elevated levels of all four enzymes were found when cells were grown with acetate as a primary carbon and energy source, and even higher levels were observed when palmitic acid was provided as a primary carbon and energy source. High-pressure liquid chromatography was used to demonstrate that, in the presence of glucose, uniformly labeled [14C]palmitic acid was converted to intermediates of the tricarboxylic acid cycle and glyoxylate shunt. Pregrowth with palmitic acid was not required for this conversion. Strains lacking the 6- or the 47-megadalton plasmid did not take up [3H]palmitic acid but did possess levels of enzyme activity comparable to those observed in the wild-type strain.