Isolation of lipopolysaccharides and the effect of polymyxin B on the outer membrane of Corynebacterium autotrophicum.

Lipopolysaccharides (LPS) from Corynebacterium autotrophicum were isolated and analyzed. Autotrophically grown cells contained 2--5 mg of partly purified LPS per g dry weight of lyophilized cells. Serological cross reaction with Lipid A antigen of Salmonella minnesota confirmed the presence of LPS in C. autotrophicum. Electron microscopy of negatively stained Polymyxin B-treated cells showed formation of blebs on the Outer Membrane indicating an interaction of Polymyxin B specifically with LPS. Up to now, no Gram-positive organisms are known which contain any LPS. Thus, C. autotrophicum, though giving opposite results when the Gram-staining reaction was applied by several authors, has to be classified into the group of Gram-negative bacteria.