Description of sp. nov., a keratinolytic bacterium isolated from a freshwater river.

A Gram-stain-negative, aerobic, rod-shaped bacterial strain, designated MMS21-Ot14, was isolated from a freshwater river, and shown to represent a novel species of the genus on the basis of the results from a polyphasic approach. The 16S rRNA gene sequence analysis revealed that MMS21-Ot14 represented a member of the genus of the family and was closely related to RHA2-9 (97.52 % sequence similarity), THG A18 (97.46 %) and P 461/12 (97.27 %). The optimal growth of MMS21-Ot14 occurred at 25-30 °C, pH 6.0-7.0 and in the absence of NaCl. MMS21-Ot14 was capable of hydrolysing casein, starch, DNA, Tween 20 and tyrosine. The strain also showed keratinolytic activity with keratin azure and decolourising activity with remazol brilliant blue R (RBBR), which indicated potential ability to degrade keratin and lignin. The main polar lipids of MMS21-Ot14 were phosphatidylethanolamine, unidentified aminophospholipids, unidentified aminolipids, an unidentified phospholipid and several unidentified lipids. The predominant fatty acids of MMS21-Ot14 were iso-C and iso-C 3-OH, and the major isoprenoid quinone was menaquinone 6 (MK-6). The whole genome of MMS21-Ot14 was 5 062 016 bp in length with a DNA G+C content of 37.7 %. The average nucleotide identity and digital DNA-DNA hybridisation values between MMS21-Ot14 and phylogenetically related members of the genus were well below the threshold values for species delineation. It is evident from the results of this study that MMS21-Ot14 should be classified as representing a novel species of the genus , for which the name sp. nov. (type strain, MMS21-Ot14 = KCTC 92255 = LMG 32529) is proposed.