Loktanella hongkongensis sp. nov., a novel member of the α-Proteobacteria originating from marine biofilms in Hong Kong waters

Abstract

A Gram-negative, non-motile, non-spore-forming, short rod-shaped bacterium (UST950701-009PT) was isolated from a marine biofilm in Hong Kong waters. Colonies are pink in colour, convex with a smooth surface and entire edge. Brown diffusible pigment is produced. Whitish colonies, with otherwise identical morphology, emerge from every culture upon ageing. The white colonies can be maintained as separate cultures (UST950701-009W) without turning pink. UST950701-009PT and UST950701-009W have identical 16S rRNA gene sequences and similar G+C (65·9–66·2 mol%) and fatty acid (86·22–88·52 % 18 : 1ω7c) contents. Phylogenetic analysis of the 16S rRNA gene sequence places UST950701-009PT within the Rhodobacter group of the α-subclass of the Proteobacteria. The nearest neighbours belong to the genus Loktanella, with similarity values ranging from 94·5 to 95·5 %. Data on G+C and fatty acid contents support the affiliation to the genus Loktanella. UST950701-009PT and -009W are heterotrophic, strictly aerobic and require NaCl for growth (2·0–14·0 %). Both grow in pH 5·0–10·0 and at 8–44 °C. Both are positive in oxidase, catalase and β-galactosidase tests, but they differ in the pattern of carbohydrate oxidation and assimilation. Molecular evidence together with phenotypic characteristics shows that UST950701-009PT constitutes a novel species within the genus Loktanella. The name Loktanella hongkongensis sp. nov. is proposed; the type strain is UST950701-009PT (=NRRL B-41039T=JCM 12479T) and a morphovar is UST950701-009W (=NRRL B-41040=JCM 12480).