Sphingobacterium micropteri sp. nov. and Sphingobacterium litopenaei sp. nov., isolated from aquaculture water

Two novel bacterial strains, designated as DN00404^T and DN04309^T, were isolated from aquaculture water and characterized by using a polyphasic taxonomic approach. Cells of strains DN00404^T and DN04309^T were Gram-stain-negative, aerobic, non-motile, oxidase-positive and catalase-positive. Cells of DN00404^T were short rod-shaped and those of DN04309^T were long rod-shaped. Strain DN00404^T was found to grow at 15-37 °C (optimum, 25-30 °C), at pH 6.0-11.0 (optimum, pH 7.5) and in 0-2.0 % (w/v) NaCl (optimum, 1.0 %). Strain DN04309^T was found to grow at 15-45 °C (optimum, 20-37 °C), at pH 5.5-11.0 (optimum, 7.5) and in 0-4.0 % (w/v) NaCl (optimum, 0.5 %). Phylogenetic analyses based on 16S rRNA gene and genome sequences revealed that the two strains belonged to the genus Sphingobacterium and were distinct from all known species of this genus. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains and between each of the two strains and related type strains of this genus were well below the recognized thresholds of 95.0-96.0 % ANI and 70.0 % dDDH for species delineation. The genomic DNA G+C contents of strains DN00404^T and DN04309^T were 41.6 and 36.0 mol%, respectively. The respiratory quinone in both strains was identified as MK-7, and their major fatty acids were iso-C_15 : 0 and summed feature 3 (C_16 : 1  ω6c and/or C_16 : 1  ω7c), which were similar to those of other species of this genus. The two major fatty acids C_16 : 0 and iso-C_17 : 0 3-OH were also found in strain DN00404^T. Based on genotypic and phenotypic characteristics, two novel species of the genus Sphingobacterium are proposed: Sphingobacterium micropteri sp. nov. with DN00404^T (=GDMCC 1.1865^T=KACC 21924^T) as the type strain and Sphingobacterium litopenaei sp. nov. with DN04309^T (=GDMCC 1.1984^T=KCTC 82348^T) as the type strain.