Oceanicaulis alexandrii gen. nov., sp. nov., a novel stalked bacterium isolated from a culture of the dinoflagellate Alexandrium tamarense (Lebour) Balech

1 Division of Microbiology, German Research Centre for Biotechnology (GBF), Mascheroder Weg 1, 38124 Braunschweig, Germany 2 Fisheries Research Services, Marine Laboratory, Victoria Road, Aberdeen AB11 9DB, UK Correspondence Carsten Strömpl cst{at}gbf.de Five bacterial strains were isolated from a non-toxigenic strain of the marine dinoflagellate Alexandrium tamarense (Lebour) Balech CCMP 116 (NEPCC C116), during a survey of the diversity of bacteria associated with paralytic shellfish toxin-producing cultures of Alexandrium spp. (Dinophyta). All strains were strictly aerobic, Gram-negative, straight or curved rods. Cells were dimorphic, with stalks (or prosthecae) and non-motile or non-stalked and motile, by means of a single polar flagellum. The bacteria grew best at salt concentrations ranging from 2 to 10 % and growth occurred at 10 °C, but not at 50 °C. The G+C content of the chromosomal DNA of the strains was determined to be 61–62 mol%. Major cellular fatty acids of the bacteria presented a unique profile. 16S rRNA gene sequence analysis showed the five strains to be related to genera of budding bacteria of marine origin in the ‘Alphaproteobacteria’, namely, Hirschia , Maricaulis and Hyphomonas , although they exhibited substantial differences in morphology, substrate utilization and fatty acid profile to members of these genera. The five strains are proposed to comprise a new species of a new genus, Oceanicaulis alexandrii gen. nov., sp. nov., the type strain of which is C116-18 T (=DSM 11625 T =NCIMB 13905 T ). Published online ahead of print on 20 June 2003 as DOI 10.1099/ijs.0.02635-0. The EMBL accession numbers for the 16S rRNA gene sequences of Oceanicaulis alexandrii C116-3 and C116-18 T are AJ309863 and AJ309862 , respectively. A selection of 16S rDNA sequence stretches and helices where the five strains of O. alexandrii exhibit diagnostic differences from related genera (Table I) and characteristics useful for differentiating the genus Oceanicaulis from related genera (Table II) are available in IJSEM Online. Present address: Department of Medicine and Therapeutics, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, UK. Present address: The Macaulay Institute, Craigiebuckler, Aberdeen AB15 8QH, UK.