Metabolic Activity of the Trench Fever Rickettsia,Rickettsia quintana

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Abstract
A study of the metabolic activity ofRickettsia quintanawas carried out by conventional Warburg and radioisotope techniques with intact cells harvested while growing in the fluid counterpart of the medium of Vinson and Fuller. Like other rickettsiae,R. quintanadid not utilize glucose, but did metabolize glutamate and glutamine. Unlike typhus rickettsiae,R. quintanadid not require a diluent high in K+for metabolic activity, and it utilized glutamine more efficiently than glutamate. In typical experiments, this microorganism produced 1.6 to 2.0 μmoles of CO2from glutamine per mg of rickettsial protein per hr at 37 C, while consuming 1.5 to 1.7 μmoles of O2.R. quintanaalso utilized, in descending order, succinate, α-ketoglutarate, glutamate, pyruvate, and citrate; the first-named substrate was utilized more rapidly than glutamine.R. quintana, like typhus rickettsiae, has a glutamate-oxaloacetate transaminase because aspartate was isolated, by means of thin-layer chromatography, as one of the end products of the utilization of glutamine. When the microorganisms were incubated with glutamine-14Cand unlabeled intermediates of the citric acid cycle, labeled dicarboxylic acids of the cycle were recovered. Labeled tricarboxylic acids, however, were not recovered, possibly because of cellular impermeability to the corresponding unlabeled intermediates. In the case ofcis-aconitate, it was shown that this substrate interfered with the uptake of glutamine. These observations are believed to provide convincing evidence that glutamine is utilized through the citric acid cycle and thatR. quintana, with the differences noted, resembles other rickettsiae.