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

A Gram-stain-negative, aerobic, rod-shaped bacterial strain, designated MMS21-Ot14^T, was isolated from a freshwater river, and shown to represent a novel species of the genus Chryseobacterium on the basis of the results from a polyphasic approach. The 16S rRNA gene sequence analysis revealed that MMS21-Ot14^T represented a member of the genus Chryseobacterium of the family Weeksellaceae and was closely related to Chryseobacterium hagamense RHA2-9^T (97.52 % sequence similarity), Chryseobacterium gwangjuense THG A18^T (97.46 %) and Chryseobacterium gregarium P 461/12^T (97.27 %). The optimal growth of MMS21-Ot14^T occurred at 25-30 °C, pH 6.0-7.0 and in the absence of NaCl. MMS21-Ot14^T 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^T were phosphatidylethanolamine, unidentified aminophospholipids, unidentified aminolipids, an unidentified phospholipid and several unidentified lipids. The predominant fatty acids of MMS21-Ot14^T were iso-C_15 : 0 and iso-C_17 : 0 3-OH, and the major isoprenoid quinone was menaquinone 6 (MK-6). The whole genome of MMS21-Ot14^T 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^T and phylogenetically related members of the genus Chryseobacterium were well below the threshold values for species delineation. It is evident from the results of this study that MMS21-Ot14^T should be classified as representing a novel species of the genus Chryseobacterium, for which the name Chryseobacterium fluminis sp. nov. (type strain, MMS21-Ot14^T = KCTC 92255^T = LMG 32529^T) is proposed.