Isolation and metabolism of glycogen and poly-betahydroxybutyrate in Nocardia asteroides at different developmental stages

Sudanophilic and iodine-staining cytoplasmic granules were isolated at various developmental stages during growth of Nocardia asteroides (strain 55) and identified as poly-beta-hydroxybutyrate (PHB) and glycogen granules, respectively. During growth in nutrient broth containing 1% glucose, maximal accumulation of PHB and glycogen granules, up to 10 and 20% respectively, of its dry-weight was obtained in the filamentous cells at 16 h just prior to the onset of cell fragmentation during the stationary phase. The decrease of the cytoplasmic granules was concomitant with fragmentation of the cells to rod-like and spherical cells, suggesting that the polymers may serve as carbon and energy source during morphogenesis. Both granules were detected in the three cell-forms. At higher concentrations of glucose (4%) more glycogen granules (9 times) accumulated than PHB (4 times) and glycogen hydrolysis was also faster than that of PHB, suggesting preferences of glycogen over PHB as energy and carbon source under this growth condition. Growth and biosynthesis of granules were significantly reduced by very high glucose concentration (10%) and the usual pleomorphic developmental stages were reduced to a dimorphic life cycle. Thus, biosynthesis of both granules and morphogenesis are under catabolite repression. Both polymers were also found in N. brasiliensis and N. otitidis-caviarum, indicating that cytoplasmic accumulation of multiple granules is common in the genus.