STRAINS OF THE HALOPHILIC SPECIES RHODOBIUM-MARINUM THAT INHABIT FRESH-WATER NOT SPRINGS

Two strains of budding purple bacteria, Rhodobium sp. KR-36m and KR-54 m, were isolated from freshwater sulfur-rich hot springs (Kunashire Is land, the Kurils) and found to belong to facultative halophiles with a salinity optimum of 1-3%. By most of phenotypic criteria, these bacte ria were close to the seawater species Rbi. marinum. They oxidized sul fide to sulfur in the course of photosynthesis, and were in this respe ct similar to Rbi. marinum: although Rbi. marinum had been described a s oxidizing sulfide to sulfur and thiosulfate, the type strain Rbi, ma rinum DSM 2698 used in this work was found to oxidize sulfide only to sulfur. Based on phenotypic features and data on DNA-DNA homology, str ains KR-36m and KR-54m were assigned to the species Rbi, marinum. Acco rdingly, the diagnosis of this species should be revised as follows: ( 1) Rbi. marinum oxidizes sulfide to sulfur in the process of photosynt hesis, (2) requires thiamine and p-aminobenzoate, (3) and can inhabit freshwater environments, specifically, freshwater sulfur-rich hot spri ngs.