The cell wall of the obligate intracellular bacterial parasite of small free-living amoebae. I. Morphology and chemical composition of the rigid layer and peptidoglycan.

The obligate intracellular bacterial parasite "OIBP" of small free-living amoebae, discovered by Drozanski (1956) was propagated in axenic culture of Acanthamoeba castellanii. The peptidoglycan prepared by chemical extraction of intact cells of the bacterium was examined in a transmission electron microscope and analysed chemically. Electron micrographs of heavy metal shadowed preparations revealed a bag-shaped membraneous structure resembling that of the peptidoglycan sacculi of Escherichia coli and the other gram-negative bacteria so far studied. The peptidoglycan may be present in a lipoprotein-peptidoglycan complex, as proteolytic enzyme treatment resulted in changes of the ultrastructure and in chemical composition. Results of chemical analysis of acid hydrolysed peptidoglycan indicate the presence of two aminosugars; glucosamine and muramic acid and also significant amounts of glycine together with three major amino acids; alanine, glutamic acid and diaminopimelic acid. It was shown that the peptidoglycan was, however, resistant to the hydrolytic action of egg-white lysozyme and to the lysosomal endo N-acetylmuramidases of amoebael origin.