Ascidiimonas meishanensis sp. nov. and Leptobacterium meishanense sp. nov., two bacteria isolated from marine sediment in the East China Sea

Two Gram-stain-negative, curved-rod-shaped, non-motile and aerobic bacteria W6 T and I13 T were isolated from marine sediment samples collected from Meishan Island located in the East China Sea. Catalase and oxidase activities and hydrolysis of Tween 40, 60 and 80 were positive for both strains, while nitrate reduction, indole production, methyl red reaction and H 2 S production were negative. Phylogenetic analyses based on 16S rRNA and genome sequences revealed that strains W6 T and I13 T formed distinct phylogenetic lineages within the genera Ascidiimonas and Leptobacterium , respectively. Strain W6 T showed the closest relatedness to Ascidiimonas aurantiaca N5DA8-2C T with 93.9% 16S rRNA gene sequence similarity, 70.7% average nucleotide identity (ANI), 71.0% average amino acid identity (AAI) and 16.4% digital DNA–DNA hybridization (dDDH) values, while strain I13 T was most closely related to Leptobacterium flavescens YM3-301 T with 92.1% 16S rRNA gene sequence similarity, 70.5% ANI, 72.1% AAI and 17.2% dDDH values. The two novel strains shared 92.0% 16S rRNA gene sequence similarity to each other and were identified as two distinct species based on 70.7% ANI, 70.4% AAI and 17.1% dDDH values calculated using whole-genome sequences. The genomes of strains W6 T and I13 T were 4.59 Mbp with a G+C content of 34.5 mol% and 2.38 Mbp with a G+C content of 36.2 mol%, respectively. The only respiratory quinone was menaquinone-6, the major polar lipid was phosphatidylethanolamine and the major cellular fatty acids were iso-C 15 : 0 , iso-C 15 : 1 G and iso-C 17 : 0 3-OH. Based on phenotypic, chemotaxonomic and genotypic data, strains W6 T and I13 T are considered to represent two novel species in the genera Ascidiimonas and Leptobacterium , respectively, in the family Flavobacteriaceae, for which the names Ascidiimonas meishanensis sp. nov. and Leptobacterium meishanense sp. nov. are proposed. The type strains are W6 T (=KCTC 102201 T =MCCC 1K08928 T ) and I13 T (=KCTC 102202 T =MCCC 1K08929 T ), respectively.