Flavobacterium proteolyticum sp. nov., isolated from aquaculture water

A novel aerobic, yellow, and rod-shaped bacterial isolate, designated as 1Y8A^T, was isolated from aquaculture water sampled in Jiangmen, Guangdong province, P. R. China. Here, the taxonomic position of strain 1Y8A^T was conducted based on phenotypic, genomic, and chemotaxonomic characteristics. Strain 1Y8A^T 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 1Y8A^T was closely related to "Flavobacterium sasangense" YC6274^T (99.3%), Flavobacterium aquaticum JC164^T (98.4%), Flavobacterium cucumis R2A45-3^T (98.0%), Flavobacterium celericrescens TWA-26^T (98.0%), and Flavobacterium cheniae NJ-26^T (97.2%). The digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain 1Y8A^T 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 1Y8A^T formed an independent branch distinct from known species. The major cellular fatty acids of strain 1Y8A^T were iso-C_15:0, iso-C_15:1 G and C_15:0; 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 1Y8A^T 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 1Y8A^T (= GDMCC 1.1933^T = KACC 22081^T).