The Genus Seliberia

Abstract

Bacteria of the genus Seliberia are recognized by the presence of radial clusters (starlike aggregates) of rod-shaped bacteria, a characteristic screwlike twisting of the rod surface, and the formation of oval or spherical reproductive cells by a budding process—usually at the apical end of rods in a radially arranged aggregate or at a tip of an individual rod (Aristovskaya and Parinkina, 1963; Aristovskaya, 1964). The rods are 0.5–0.7 µm wide and their length varies with the composition of the nutrient medium used (Aristovskaya, 1974). The oval “reproductive” cells, which are found in soil isolates cultivated on appropriate medium, may also occur in the center of the star-shaped aggregates, and these “reproductive” cells have been observed to germinate into rods. A preponderance of oval cells or spherical cells is referred to as the zoogleal stage. The spherical or oval cells of Seliberia stellata, a soil isolate, and several seliberia-like helically sculptured rods of aquatic origin are not observed when isolated strains of these bacteria are cultivated on dilute peptone or other routine laboratory maintenance media, rather than on soil extract medium; the rods then divide by transverse asymmetric binary fission. The small, rod-shaped daughter cells, released from the aggregate, are motile by a subpolar flagellum and later may attach to a substrate by means of a polar holdfast. These bacteria are Gram negative. Dichotomous branching is occasionally observed (Aristovskaya and Parinkina, 1963; J. R. Swafford, unpublished observations). The ability to accumulate ferric hydroxide is characteristic.