TOW NOVEL STRAINS BELONGING TO A NOVEL GENUS IN THE FIRMICUTES AND A NOVEL SPECIES IN THE TISSIERELLA, ISOLATED FROM DESALINATION PROCESS

초록

In order to determine microbial communities of reverse osmosis (RO) based desalination process, culture-dependant and -independent approaches were performed. In this study, two isolates, strains R7 and R4 were isolated from intake seawater and the strains belonged to a novel species in Tissierella (R7) and a novel genus in the Firmicutes (R4), respectively. mPlate Count Broth (mPCB) and R2A medium were modified by addition of sodium chloride (3.5%) and filter sterilized seawater (5%). Samples from RO plant (intake seawater, particle suspensions from prefilter and RO membrane) were serially diluted and plated on modified mPCB and R2A agar media. The 16S rRNA sequences of the two strains were phylogenetically analyzed and physiological and biochemical characteristics were also determined. Strain R4 is distinguished from other members of the Firmicutes by ca. 10% 16S rRNA sequence dissimilarity. Phylogenetic trees showed the placement of strain R4 in the Firmicutes as a novel genus. Strain R7 is Gram-staining-negative and non-sporulating bacterium. 16S rRNA gene sequence analyses indicated that strain R7 is closely related to other species of the genus Tissierella, but the sequence divergence was more than 5%. Phenotypic characteristics of strain R7 also showed clear distinction from other Tissierella species. Based on 16S rRNA sequence analysis and phylogenetic evidence, a novel genus in the Firmicutes and a novel species in the Tissierella, are proposed.