Morphological Changes in Poly-β-Hydroxybutyrate Granules Associated with Decreased Susceptibility to Enzymatic Hydrolysis

Merrick, J. M. (State University of New York, Buffalo), D. G. Lundgren, and R. M. Pfister. Morphological changes in poly-β-hydroxybutyrate granules associated with decreased susceptibility to enzymatic hydrolysis. J. Bacteriol. 89:234–239. 1965.—A complex enzyme system obtained from extracts of Rhodospirillum rubrumcells hydrolyzes poly-β-hydroxybutyric acid (PHB) contained in native PHB granules isolated from Bacillus megaterium. A labile factor associated with the granules and necessary for depolymerization is easily destroyed by various chemical and physical treatments. Granules inactivated by these treatments were examined in an electron microscope. In all cases, the distinct morphological appearance of native granules was altered. Morphological changes were mainly characterized by membrane fragmentation, loss of coalescence, and surface alterations. These observations suggest that native PHB granules possess definite structural features, disruption of which results in decreased susceptibility of the polymer to enzymatic hydrolysis.