Poly- -hyroxybutyrate Metabolism in Washed Suspensions of Bacillus cereus and Bacillus megaterium

Abstract

SUMMARY: Poly-β-hy droxybutyrate has been previously shown to be a major component of bacterial ‘lipid’ granules. In the present study, the conditions under which it was formed and degraded by Bacillus cereus and B. megaterium were studied in washed suspensions. Suitable substrates for synthesis were glucose, pyruvate or β-hy droxybutyrate. Acetate, although alone unable to induce synthesis, greatly enhanced formation in presence of these substrates. Under optimal conditions, suspensions synthesized up to eight times their original content of poly-β-hydroxy- butyrate in 4 hr. Formation was inhibited by high concentrations of oxygen, although no synthesis occurred anerobically in nitrogen. The optimal concentration of oxygen was about 5% . B. cereus only was able to synthesize poly-β-hydroxybutyrate in an atmosphere of hydrogen. In the absence of an external carbon and energy source, degradation occurred rapidly aerobically, to carbon dioxide and water, and more slowly anaerobically to β-hydroxybutyrate and acetoacetate. The evidence that poly-β-hydroxybutyrate is a reserve carbon and energy source is discussed.