REGULATION OF POLY(BETA-HYDROXYBUTYRATE) SYNTHESIS IN METHYLOBACTERIUM-RHODESIANUM MB-126 GROWING ON METHANOL OR FRUCTOSE

The intracellular concentration of CoA metabolites and nucleotides was determined in batch cultures of Methylobacterium rhodesianum grown on methanol and shifted to growth on fructose. The intracellular concent ration of CoA decreased from a high value of 0.6 nmol/mg poly(beta-hyd roxybutyrate)-free bacterial dry mass during growth on methanol to a l ow value of 0.03 nmol/mg poly(beta-hydroxybutyrate)-free bacterial dry mass after a shift to fructose as a carbon source. The levels of NADH , NADPH, and acetyl-CoA were also lower. Under these conditions, acety l-CoA was metabolized by both citrate synthase and beta-ketothiolase, and poly(beta-hydroxybutyrate) synthesis and growth occurred simultane ously during growth on fructose. Moreover, the level of ATP was approx imately 50% lower during growth on fructose, supporting the hypothesis of a bottleneck in the energy supply during the growth of M. rhodesia num with fructose.