PYRUVATE METABOLISM IN HALOBACTERIUM-SALINARIUM STUDIED BY INTRACELLULAR C-13 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

C-13 nuclear magnetic resonance spectroscopy was used to study the met abolism of [2-C-13]pyruvate in intact cells of Halobacterium salinariu m. The spectra of these cells show that pyruvate is reduced to lactic acid and transaminated to alanine. The intensity of C-2 lactate is hig her under anaerobic conditions than under aerobic conditions. When cel ls are grown in the absence of glucose, the level of C-2 lactate inten sity is lower. In extracts of these cells, the level of NADH-dependent lactate dehydrogenase activity is lower than that of cells grown in t he presence of glucose. A C-5 glutamate resonance suggests the entry o f pyruvate into the tricarboxylic acid cycle through acetyl-coenzyme A . In addition, the label is also observed at C-3 and C-4 of glutamate, signifying a pyruvate carboxylase-type reaction and scrambling of lab el at the fumarate-succinate stage plus malic enzyme operation, respec tively. Citrate synthase and malic enzyme activity appear to be contro lled by the growth conditions of H. salinarium.