Gluconate metabolism of Klebsiella pneumoniae NCTC 418 grown in chemostat culture.

The metabolism of gluconate by Klebsiella pneumoniae NCTC 418 was studied in continuous culture. Under all gluconate-excess conditions at low culture pH values (pH 4.5-5.5) the majority (70-90%) of the gluconate metabolized was converted to 2-oxogluconate via gluconate dehydrogenase (GADH), although specific 2-oxogluconate production rates under potassium-limited conditions were significantly lower than under other gluconate-excess conditions. At high culture pH values, metabolism shifted towards production of acetate. Levels of GADH were highest at low culture pH values and synthesis was stimulated by the presence of (high concentrations of) gluconate. An increase in activity of the tricarboxylic acid cycle was accompanied by a decrease in GADH activity in vivo and in vitro, suggesting that the GADH serves a role as an alternative energy-generating system. Anaerobic 2-oxogluconate production was found to be possible in the presence of nitrate as electron acceptor. Levels of gluconate kinase were highest when K. pneumoniae was grown under gluconate-limited conditions. Under carbon-excess conditions, levels of this enzyme correlated with the intracellular catabolic flux.