Formation of intracytoplasmic membranes in chemotrophic mecillinam sphaeroplasts of Rhodospirillum rubrum.
Chemotrophically growing cells of Rhodospirillum rubrum were transformed into sphaeroplasts of irregular shape under the influence of the penicillin antibiotic mecillinam. On a cell protein basis, respiratory activities of whole sphaeroplasts were slightly decreased as compared with the untreated control. But, on a membrane protein basis various activities of the respiratory chain were largely identical in membrane preparations from untreated cells and sphaeroplasts, respectively. Chemotrophically cultured sphaeroplasts did not produce detectable quantities of bacteriochlorophyll. Nevertheless, electron-microscopic examination of thin sections and freeze fractures revealed the presence of vesicular intracytoplasmic membranes in the major portion of sphaeroplasts. The diameter of these vesicles was smaller (35-40 nm) than that of the vesicles formed under phototrophic conditions (60-70 nm). A minor portion of the sphaeroplasts contained large amounts of membraneous extrusions in the enlarged periplasmic space. Upon removal of mecillinam, the sphaeroplasts were reverted into normal cells exhibiting no intracytoplasmic membranes under chemotrophic conditions. Only a few sphaeroplasts were unable to revert; these sphaeroplasts, however, still increased the cellular amounts of membraneous structures.
D001429:Bacteriochlorophylls / Q000096:biosynthesis; D002454:Cell Differentiation; D007425:Intracellular Membranes / Q000648:ultrastructure*; D008854:Microscopy, Electron; D010101:Oxygen Consumption; D010788:Photosynthesis; D012247:Rhodospirillum rubrum / Q000502:physiology / Q000648:ultrastructure*
D001429:Bacteriochlorophylls