Jannaschia cystaugens sp. nov., an Alexandrium (Dinophyceae) cyst formation-promoting bacterium from Hiroshima Bay, Japan

Abstract

Heterotrophic bacteria isolated from water samples taken from Hiroshima Bay, Japan, and referred to as Alexandrium (Dinophyceae) cyst formation-promoting bacteria, were assigned to the Roseobacter–Sulfitobacter–Silicibacter group within the α-Proteobacteria on the basis of nearly complete 16S rRNA gene sequences. Phylogenetic analyses showed that two strains, CFPB-A9T and CFPB-A5, are closely related to each other and that their closest relative was Jannaschia helgolandensis (95·9 % sequence similarity). These strains were Gram-negative, motile, obligately aerobic rods that required sodium ions and 2–7 % sea salts for growth and did not produce bacteriochlorophyll a. Their optimal growth temperature was 25–30 °C. The strains had Q-10 as the dominant respiratory quinone. Primary cellular fatty acid in both strains was 18 : 1ω7c. The DNA G+C contents of strains CFPB-A9T and CFPB-A5 were 59·1 and 59·2 mol%, respectively. Based on physiological, biological, chemotaxonomic and phylogenetic data, the strains are considered to represent a novel species, Jannaschia cystaugens sp. nov., with type strain CFPB-A9T (=LMG 22015T=NBRC 100362T).