Metabolite concentrations in Alcaligenes eutrophus H 16 and a mutant defective in poly-beta-hydroxybutyrate synthesis

Abstract

Intracellular concentrations of hexose phosphates, phosphoenolpyruvate, pyruvate, NAD(H) and NADP(H) as well as the protein and poly-beta-hydroxybutyrate (PHB) content were measured in suspensions of autotrophically grown cells of Alcaligenes eutrophus H 16 and compared with those in a mutant unable to synthesize poly-beta-hydroxybutyrate. The parent strain was subjected to successive changes in conditions, and new steady states were rapidly (~20 min) attained. When the parent strain was provided with carbon and energy but no nitrogen source, it fixed CO2 and accumulated large amounts of PHB. When the mutant PHB-4 was exposed to identical conditions, no accumulation of PHB occurred, but pyruvate, malate and citrate were excreted, and a 6-fold accumulation of hexose monophosphate (over the levels in the parent) was observed: in contrast, cofactors in intermediates between fructose-1,6-phosphate and phosphoenolpyruvate reached steady state as in the parent strain. When ammonium ion was then supplied, growth started and the metabolite concentrations in the mutant returned to the levels observed in the parent strain.