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

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 alpha-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 degrees C. The strains had Q-10 as the dominant respiratory quinone. Primary cellular fatty acid in both strains was 18 : 1omega7c. 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).