Flavihumibacter fluminis sp. nov., a novel thermotolerant bacterium isolated from river silt

A yellow, Gram- stain-positive, strictly aerobic, thermotolerant, non-motile and rod-shaped bacterial strain, designated RY-1T, was isolated from a silt sample of Fuyang River, Wuqiang County, Hengshui City, Hebei Province, PR China. Cells showed oxidase-and catalase-positive activities. Growth occurred at 20-45 degrees C (optimum, 37 degrees C) and pH 6.0-8.0 (optimum, pH 7.0), and in the presence of 0-1.5 % (w/v) NaCl (optimum, 0%). A phylogenetic tree based on 16S rRNA gene sequences revealed that strain RY-1T formed a phylogenetic lineage with Flavihumibacter members within the family Chitinophagaceae. A comparison of 16S rRNA gene sequences showed that strain RY- 1T was most closely related to Flavihumibacter cheonanensis WS16T (98.6 %), Flavihumibacter sediminis CJ663T (97.7 %) and Flavihumibacter solisilvae 3-3T (97.6 %). The genome size of strain RY- 1T was 4.71 Mb, and the DNA G+C content was 44.3 %. The average nucleotide identity, digital DNA-DNA hybridization and average amino acid identity values between strain RY- 1T and reference strains were all lower than the threshold values for species delineation. Strain RY-1T contained menaquinone- 7 and iso-C15:0, iso-C17: 0 3 -OH and iso-C15:1G as the sole respiratory isoprenoid quinone and major cellular fatty acids (>= 5 %), respectively. The major polar lipids consisted of phosphatidylethanolamine, three unidentified aminolipids and four unidentified lipids. According to the results of phenotypic, phylogenetic and chemotaxonomic characteris-tics, strain RY- 1T represents a novel species of the genus Flavihumibacter, for which the name Flavihumibacter fluminis sp. nov. is proposed. The type strain is RY- 1T (=GDMCC 1.2775T=JCM 34870T).