Ornithinimicrobium tianjinense sp. nov., isolated from a recirculating aquaculture system

Abstract

A Gram-positive, strictly aerobic and heterotrophic, non-spore-forming actinobacterium (strain B2T) isolated from a recirculating aquaculture system was studied for its taxonomic position. Strain B2T formed a rudimentary substrate-mycelium that fragmented into short rod-shaped to coccoid cells (0.5 µm×0.5–2.2 µm or 0.5–1.0 µm in diameter). Colonies were yellow, smooth, circular and 1.5–2.0 mm in diameter after incubation on TSA for 3 days at 30 °C. Strain B2T grew at 20–40 °C (optimal, 30 °C) and pH 5.5–9.5 (optimal, 6.5–7.0) and in the presence of 0–9 % (w/v) NaCl (optimal, 1 %). The predominant menaquinone of strain B2T was MK-8(H4). The cell-wall peptidoglycan of strain B2T contained the amino acids ornithine, glutamic acid, alanine, glycine and aspartic acid. The major polar lipids were phosphatidylglycerol and diphosphatidylglycerol. The major fatty acids were iso-C15 : 0, iso-C16 : 0 and summed feature 9. Its DNA G+C content was 68.3 mol% (T m). Analysis of 16S rRNA gene sequences indicated that strain B2T was related phylogenetically to members of the genus Ornithinimicrobium with highest similarity (96.6 %) to Ornithinimicrobium kibberense DSM 17687T, followed by Ornithinimicrobium humiphilum DSM 12362T (96.3 %), Ornithinimicrobium pekingense LW6T (96.2 %) and Ornithinimicrobium murale 01-Gi-040T (94.8 %). On basis of phenotypic, chemotaxonomic and phylogenetic data, it was concluded that strain B2T represents a novel species of the genus Ornithinimicrobium , for which the name Ornithinimicrobium tianjinense sp. nov. is proposed. The type strain is B2T ( = CGMCC 1.12160T = JCM 18464T).