Effects of intracellular poly(3-hydroxybutyrate) reserves on physiological–biochemical properties and growth of Ralstonia eutropha

Microbial polyhydroxyalkanoates (PHAs), because of their well studied complex physiology and commercial potential, are vehicles for carbon and potential storage reduction for many microbial species. Even with the wealth of studies about microbial PHAs in the scientific literature, polymer accumulation and degradation are still not comprehensively understood. Poly(3-hydroxybutyrate) (P3HB) granule formation and polymer mobility were studied here in the bacterium Ralstonia eutropha strain B5786 in autotrophic cultures. Electron microscopy studies revealed decreasing cell size concomitant with enlargement of size and number of intracellular granules, and inhibition of cell division during intracellular polymer production. Activities of key P3HB biosynthetic enzymes demonstrated correlations with each other during polymer accumulation, suggesting an intricately regulated P3HB cycle in autotrophically grown R. eutropha cells.