SARCOBIUM-LYTICUM GEN-NOV, SP-NOV, AN OBLIGATE INTRACELLULAR BACTERIAL PARASITE OF SMALL FREE-LIVING AMEBAS

A new genus and species of obligate intracellular bacterial parasite of small free-living amoebae is described. This bacterium causes fatal infections in amoebae belonging to the Acanthamoeba-Naegleria group. It does not grow on any artificial substrate deprived of living amoeba cells. The entry of the bacterium into a host occurs by phagocytosis, but growth occurs in the cytoplasm, not in phagosomes. This parasite is readily distinguished from other kinds of previously recognized bacteria that live within amoeba cells on the basis of its host cell lytic activity. The bacterium is a gram-negative, short rod with tapered ends. It multiples intracellularly by a transverse central pinching-off process. Cells are motile by means of a polar tuft of flagella. The bacterium is surrounded by a distinct multilayered cell envelope with a chemtype A1-gamma-peptidoglycan. The peptidoglycan is unique in its high content of glucosamine residues with free amino groups. The DNA base composition of this organism is 43 mol% guanine plus cytosine. The name Sarcobium lyticum gen. nov., sp. nov. is proposed for this bacterium. The type strain of S. lyticum is strain L2 (= PCM 2298).