Flavobacterium limicola sp nov., a psychrophilic, organic-polymer-degrading bacterium isolated from freshwater sediments

Three novel strains of cold-adapted bacteria, ST-82(T), ST-10 and ST-92, were isolated from freshwater sediments. These three isolates were very similar to each other in phenotypic and chemotaxonomic traits, as well as in 16S rDNA sequence. The strains were Gram-negative, elongated filament-like rods that formed bright yellow colonies. They showed neither flexirubin pigments nor gliding motility. The strains were able to hydrolyse casein, gelatin, starch, agar, aesculin, urea, uric acid and tyrosine. They also lysed cells of Escherichia coli and Pseudomonas putida. The temperature range for growth was 0-25degreesC, with optimum growth occurring at 15-20degreesC. For all isolates, protease secretion increased as temperature decreased. Sodium chloride inhibited their growth, although the strains tolerated up to 1(.)5 % (w/v) NaCl. Menaquinone-6 was the major respiratory quinone. The major cellular fatty acids were C-15:0, iso-C-15: 0, anteiso-C-15:0, C-15:1, iso-C-15:1, C(16:1)omega7cis, iso-C-16:1, iso-C-17:1, iso-C-15:0 3-OH and iso-C-16:0 3-OH. The DNA G + C content was 34(.)0-34(.)8 mol%. Phylogenetic analysis based on 16S rDNA sequences suggested that the strains belonged to the genus Flavobacterium and were closely related to Flavobacterium xanthum and Flavobacterium frigidarium, with sequence similarities of 96(.)9 and 96(.)3%, respectively. In physiological and biochemical analyses, the isolates were differentiated from all known members of the genus Flavobacterium. The name Flavobacterium limicola is proposed for these novel strains, and the type strain is ST-82(T) (=JCM 11473(T) = DSM 15094(T)).