Nioella ostreopsis sp. nov., isolated from toxic dinoflagellate, Ostreopsis lenticularis

Abstract

A novel short-rod-shaped bacterial strain with poly-β-hydroxybutyric acid granules inside, designated as Z7-4T, was isolated from a culture of a marine dinoflagellate with palytoxin-producing capacity, Ostreopsis lenticularis OS06, collected from the East China Sea. Cells of Z7-4T were Gram-stain-negative, non-motile, strictly aerobic, 0.9–1.2 µm wide and 2.0–3.9 µm long. Growth occurred in 1–4 % (w/v) NaCl, at 15–37 °C and at pH 5.0–10.0, with optimum growth in 3.5 % (w/v) NaCl, at 30 °C and at pH 7.0. Analysis of 16S rRNA gene sequence revealed that Z7-4T shared the highest 16S rRNA gene sequence similarities with Nioella aestuarii JCM 30752T (98.8 %), followed by Nioella sediminis KCTC 42144T (98.6 %) and Nioella nitratireducens KCTC 32417T (96.9 %). Phylogenetic analysis based on nearly complete 16S rRNA gene sequences revealed that Z7-4T clearly represented a member of the genus Nioella within the family Rhodobacteraceae . The respiratory quinone of Z7-4T was identified as Q-10. Polar lipids of Z7-4T were phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, three unidentified aminophospholipids and one unidentified phospholipid. The major fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0. The DNA G+C content of Z7-4T was 63.0 mol%. DNA–DNA hybridization values of the isolate against the closely related type strains were far below the 70 % limit for species delineation. The average nucleotide identity and in silico DNA–DNA genome hybridization relatedness between Z7-4T and the closely related members of the genus Nioella , N. sediminis KCTC 42144T and N. nitratireducens KCTC 32417T, were 91.1 and 46.3 %, and 79.3 and 19.4 %, respectively. On the basis of the results of polyphasic analysis, Z7-4T is proposed to represent a novel species of the genus Nioella , for which the name Nioella ostreopsis sp. nov. is proposed. The type strain of Nioella ostreopsis is Z7-4T (=KCTC 62459T=CCTCC AB 2017231T)