Glutamate Catabolism ofRickettsia rickettsiand Factors Affecting Retention of Metabolic Activity

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Abstract
Glutamate catabolism and the factors contributing to metabolic stability of purified suspensions ofRickettsia rickettsiwere investigated. By use of14C-glutamate, it was shown that CO2was produced from all carbons of glutamate and that14CO2production was reduced by the addition of most of the unlabeled intermediates of the citric acid cycle and pyruvate. Oxalacetate, added in various concentrations, did not stimulate glutamate utilization. When the cells were suspended in bovine plasma albumin (BPA), CO2production from glutamate proceeded at a nearly uniform rate for 8 hr at 32 C and for 24 hr at 15 C. When BPA was used, the cells retained their metabolic activity at 0 or 30 C regardless of cell concentration, and were not influenced by the addition of varoius metabolites. Without BPA, metabolic stability was directly related to concentration. Of the stabilizers tested on low concentrations of rickettsiae, reduced glutathione was the most effective, provided that the gas phase contained predominantly N2. Under these conditions of low partial pressure of O2, glutamate further stabilized metabolic activity and was actively metabolized. The cells were also stabilized by oxidized glutathione in a gas phase of air, but under these conditions glutamate was utilized at a more moderate rate and it impaired metabolic stability.

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