Ultrastructure of two species of halobacterium

Abstract

The morphology of a halobacterium from the Dead Sea has been compared with Halobacterium halobium. A freeze-fracture study has revealed two hexagonal patterns with repeating distances of 155 A and 65 A within layers of the cell-envelope. The larger pattern is a characteristic of the genus Halobacterium. The smaller has been identified with a surface of the cell-membrane. By the same freeze-fracture technique, the membrane adjacent to the cell-envelope was shown to be characterized by two particulate fracture faces, presumably within the hydrophobic region of the membrane. The Dead Sea Halobacterium was shown to contain poly-β-hydroxybutyric acid (PHB). Freeze-fractured cells contained granules similar to PHB granules found in other bacterial species. Alterations in the physiological state of the Dead Sea Halobacterium were found to have little effect on cell structure which was also unaffected by depletion of cell K.