Ultrastructural studies of an aquatic bacterium, seliberia stellata

Abstract

Seliberia stellata is a bacterium first isolated from tundra soil and described as a spirally twisted rod having one subpolar flagellum and reproducing by fission or budding. The cells stick at their poles forming a rosette or star form. Although this procaryotic organism has been noted in aquatic environments such as fresh water ponds and laboratory distilled water, strains from these habitats have apparently not been obtained in pure culture. We have isolated the bacteria from two fresh water sources and maintained them as pure cultures in dilute peptone-yeast extract broth or 1% agar media.Isolation of two strains of these organisms was achieved by enriching water samples with 0. 005% peptone. Enrichment culture surfaces were evaluated for the presence of bacteria by placing carbon-stabilized formvar grids onto the unbroken surface film followed by immediate removal and staining with 0. 25 or 0. 5% potassium phosphotungstate for TEM. The occurrence of Seliberia-like cells in these enrichments was rare (approximately 1/1000).