Metabolism and Transport of Purine Nucleosides by Membrane Preparations of Micrococcus sodonensis

The uptake and metabolism of adenosine-8-14C was studied using isolated membrane vesicles prepared from Micrococcus sodonensis. When the adenosine concentration was 1.0 mM, a concentration that caused prolonged bacteriostasis in growing cells, the membranes vesicles initially accumulated adenosine and inosine to similar levels but rapidly became enriched with inosine. However, when the external adenosine concentration was lowered to 0.1 mM, the vesicle contents were almost entirely inosine. No compounds other than adenosine and inosine were detected. These effects were shown to be the result of a membrane-bound adenosine deaminase and are in marked contrast to the phosphoribosyltransferase-linked mechanisms of purine nucleoside transport in other bacterial systems.