Flavobacterium proteolyticum sp. nov., isolated from aquaculture water.

A novel aerobic, yellow, and rod-shaped bacterial isolate, designated as 1Y8AT, was isolated from aquaculture water sampled in Jiangmen, Guangdong province, P. R. China. Here, the taxonomic position of strain 1Y8AT was conducted based on phenotypic, genomic, and chemotaxonomic characteristics. Strain 1Y8AT was observed to grow at 10-37 °C (optimum 28 °C), at pH 6.0-9.0 (optimum 7.0) and in 0-2% NaCl (optimum 1%, w/v). The 16S rRNA gene-based analysis showed that strain 1Y8AT was closely related to "Flavobacterium sasangense" YC6274T (99.3%), Flavobacterium aquaticum JC164T (98.4%), Flavobacterium cucumis R2A45-3T (98.0%), Flavobacterium celericrescens TWA-26T (98.0%), and Flavobacterium cheniae NJ-26T (97.2%). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain 1Y8AT and reference strains above were far below the recognized thresholds of 70% dDDH and 95-96% ANI for species definition, implying that the strain represents a novel genospecies. The phylogenomic analysis indicated that strain 1Y8AT formed an independent branch distinct from known species. The major cellular fatty acids of strain 1Y8AT were iso-C15:0, iso-C15:1 G and C15:0; the polar lipids comprised phosphatidylethanolamine, glycolipid, and two lipids; the respiratory quinone was MK-6. The G + C content of genomic DNA was 32.5%. Based on the genotypic and phenotypic characteristics such as the utilization of D-glucose and casein hydrolysis, strain 1Y8AT is concluded to represent a novel species of the genus Flavobacterium, for which the name Flavobacterium proteolyticum sp. nov. is proposed. The type strain of the species is 1Y8AT (= GDMCC 1.1933T = KACC 22081T).