Sediminibacterium planctonicum sp. nov. and Sediminibacterium longum sp. nov., isolated from surface lake and river water

Two aerobic, Gram-stain-negative, motile, rod-shaped bacteria, designated as strains TEGAF015^T and KACHI17^T, were isolated from surface lake and river waters in Japan. Strains TEGAF015^T and KACHI17^T had cell dimensions of ~0.4-0.6×1.3-2.9 µm and 0.4-0.5×2.5-4.8 µm (width×length), respectively. Strain KACHI17^T was positive for casein hydrolysis, whereas strain TEGAF015^T was negative. Phylogenetic analyses based on the 16S rRNA gene (1,290 bp) and 120 ubiquitous single-copy protein-encoding genes (5,035 aa) revealed that TEGAF015^T and KACHI17^T formed clusters closely related to <i>Sediminibacterium salmoneum</i> NJ-44^T and <i>Sediminibacterium goheungense</i> HME7863^T, respectively. However, the average nucleotide identity by orthology, average amino acid identity and digital DNA-DNA hybridization values confirmed that the isolates represent distinct species from closest phylogenetic relatives. The major cellular fatty acids identified in both strains included iso-C_15:0, iso-C_15:1 G, anteiso-C_15:0 and iso-C_17:0 3-OH. Additionally, TEGAF015^T contained anteiso-C_15:1 A, iso-C_15:0 3-OH and iso-C_16:0 3-OH. Phosphatidylethanolamine was identified as the major polar lipid of strains TEGAF015^T and KACHI17^T, which also contained menaquinone-7 as the predominant respiratory quinone and had DNA G+C contents of 38.5 and 40.0 mol%, respectively. Genome sequencing of the two isolates revealed genome sizes of 3.06 and 3.14 Mbp, respectively. Furthermore, both isolates were capable of converting dissolved organic nitrogen into ammonium during growth. These results indicated that strains TEGAF015^T and KACHI17^T represent two distinct novel species within the genus <i>Sediminibacterium</i>. The proposed names are <i>Sediminibacterium planctonicum</i> sp. nov. (type strain TEGAF015^T=JCM 16661^T=NCIMB 15525^T) and <i>Sediminibacterium longum</i> sp. nov. (type strain KACHI17^T=JCM 36264^T=LMG 33984^T).