[Regulation of citrate synthase in facultative methylotrophic bacteria]

Commonly the TCA cycle fulfils an anabolic and a catabolic function in case of aerobic chemoorganoheterotrophic nutrition. In methylotrophic growth the TCA cycle is dispensable as a bioenergetic pathway. This is reflected by properties of citrate synthase in facultative methylotrophic bacteria. Two citrate synthases, a "chemoorganoheterotrophic" one, which is inhibited by NADH (or ATP in Acetobacter MB 58), and a "methylotrophic" one, which is not or less affected by energy indicators, were found in Pseudomonas oleovorans, Pseudomonas MS, Pseudomonas MA, and Acetobacter MB 58. The concentration of these citrate synthases depends on the manner of nutrition. Bacteria with ICL-negative-variant of the serine pathway and with ribulosebisphosphate pathway seem to possess only a "chemoorganoheterotrophic" citrate synthase. Possibly the anabolic function of this citrate synthase can be realized by metabolites.