STUDIES ON THE MECHANISM OF ACETATE OXIDATION BY MICROCOCCUS LYSODEIKTICUS

Abstract

The simultaneous oxidation of labeled acetate and various unlabeled compounds postulated as components in C4 and C& metabolic cycles has been studied in previous researches with a strain of Escherichia wli which required adaptation to oxidize acetate rapidly (1).In this paper are described results obtained when the same experimental procedures were applied to a strain of Micrococcus lysodeikticus which oxidized acetate rapidly without requiring adaptation.Data obtained on the simultaneous oxidation of 2-C4-acetate and unlabeled cr-ketoglutarate, succinate, fumarate, malate, and pyruvate, singly or in combination, are presented and compared with data obtained previously with E. COG.Methods and Materials M. lysodeikticus was cultured and harvested as described by Krampitz and Werkman (2).Such cells were found to attack acetate readily.The same separation and distillation procedures were used as in the previous work (l), except in the case of a-ketoglutaric acid.Because this Cs keto acid appeared to be involved in the oxidation of acetate, it was necessary to characterize adequately the Cl4 content of this compound.This was done without isolation as follows: After acidification and removal of cells, steam distillation removed residual acetic acid.The residue was extracted for 72 hours with ether in the presence of bisulfite at pH 2 to 3. The water layer contained residual or-ketoglutaric acid free of any labeled succinate.This solution was boiled to remove SO2 and oxidized with acid permanganate to succinate and COZ.The carbonate was trapped in alkali; the succinate was extracted with ether, oxidized with a succinoxidase preparation from beef heart, and degraded with acid permanganate in the usual manner.Experiments were also conducted with pyruvate and ac-ketoglutarate added simultaneously as carriers.In order to separate the two keto