Sulfolobicins, specific proteinaceous toxins produced by strains of the extremely thermophilic archaeal genus Sulfolobus

Several novel strains of "Sulfolobus islandicus" produced proteinaceous tox ins, termed sulfolobicins, which killed cells of other strains of the same species, as well as of Sulfolobus solfataricus P1 and Sulfolobus shibatae B 12, but not of the producer strains and of Sulfolobus acidocaldarius DSM639 . The sulfolobicin purified from the strain HEN2/2 had a molecular mass of about 20 kDa. It was found to be associated with the producer cells as well as with cell-derived S-layer-coated spherical membrane vesicles 90 to 180 nm in diameter and,vas not released from the cells in soluble form.