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 TEGAF015T and KACHI17T, were isolated from surface lake and river waters in Japan. Strains TEGAF015T and KACHI17T 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 KACHI17T was positive for casein hydrolysis, whereas strain TEGAF015T 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 TEGAF015T and KACHI17T formed clusters closely related to Sediminibacterium salmoneum NJ-44T and Sediminibacterium goheungense HME7863T, 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-C15:0, iso-C15:1 G, anteiso-C15:0 and iso-C17:0 3-OH. Additionally, TEGAF015T contained anteiso-C15:1 A, iso-C15:0 3-OH and iso-C16:0 3-OH. Phosphatidylethanolamine was identified as the major polar lipid of strains TEGAF015T and KACHI17T, 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 TEGAF015T and KACHI17T represent two distinct novel species within the genus Sediminibacterium. The proposed names are Sediminibacterium planctonicum sp. nov. (type strain TEGAF015T=JCM 16661T=NCIMB 15525T) and Sediminibacterium longum sp. nov. (type strain KACHI17T=JCM 36264T=LMG 33984T).