Metabolic Studies of Rickettsiae

Abstract

Summary The preparation of purified suspensions of Rickettsia mooseri in a metabolically active state has been described. A rough correlation was found to obtain between total nitrogen content of the suspensions and (a) rate of glutamate oxidation, (b) amount of complement-fixing antigen, and (c) toxin titer. An attempt has been made to estimate the relative amount of certain host cell contaminants in the rickettsial suspensions by assay of an enzyme, cytochrome oxidase, which is associated with specific particulate fractions of the yolk sac material. These particles are concentrated by differential centrifugation along with the rickettsiae and are reduced in amount by subsequent procedures. The residual cytochrome oxidase measured is probably not a constituent part of the rickettsiae. Catalase and adenosinetriphosphatase are present in both rickettsial and control preparations. The former is reduced in amount during the purification process at roughly the same rate as cytochrome oxidase, whereas the latter appears in both normal and infected preparations in amounts greater than would be anticipated were it entirely associated with the same particulate matter as cytochrome oxidase. Studies in the analytical centrifuge have demonstrated the presence of a particulate contaminant in the final rickettsial suspensions. Optimal concentrations of substrate, PO≡4, Mg++ and Mn++ as well as optimal hydrogen ion concentration have been determined for the oxidation of glutamate by these suspensions. The gross effects on glutamate oxidation of a number of antimicrobial agents and of certain enzyme inhibitors have been studied. The antibiotic substances with marked therapeutic value in rickettsial diseases do not affect appreciably this metabolic function. On the other hand, certain common enzyme inhibitors, such as, arsenite, malonate, cyanide, fluoride and selenite, produced variable degrees of inhibition.