Marinobacter algicola sp. nov., isolated from laboratory cultures of paralytic shellfish toxin- producing dinoflagellates David H. Green, 1 John P. Bowman, 2 Elizabeth A. Smith, 3 Tony Gutierrez 1 and Christopher J. S. Bolch 4 Correspondence David H. Green david.green@sams.ac.uk 1 Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, UK 2 Australian Food Safety Centre, University of Tasmania, Hobart, Australia 3 Fisheries Research Services Marine Laboratory, Aberdeen AB11 9DB, UK 4 School of Aquaculture, University of Tasmania, Launceston, Australia Phylogenetic and phenotypic analysis of cultivable marine bacteria isolated from laboratory cultures of two paralytic shellfish toxin-producing dinoflagellates, Gymnodinium catenatum and Alexandrium tamarense, showed the presence of a novel group of Gram-negative, aerobic, moderately halophilic and hydrocarbon-degrading bacteria, related to the genus Marinobacter. The strains, designated DG893 T , DG1136 and ATAM407-13, grew optimally in media with 3–6 % NaCl and at 25–30 6C, and all could utilize n-hexadecane and n-tetradecane as the sole carbon source. The strains had a 16S rRNA gene sequence similarity of 94?2–94?3 % to Marinobacter hydrocarbonoclasticus ATCC 27132, and a similarity of 97?5–97?8 % to the closest phylogenetically related type strain, Marinobacter flavimaris DSM 16070 T . DNA–DNA hybridization levels to M. flavimaris and other Marinobacter type strains were ¡42 %, while DNA–DNA reassociation values among DG893 T , DG1136 and ATAM407-13 were ¢83 %. The DNA G+C content was 54–55 mol% and the major isoprenoid quinone was ubiquinone-9. On the basis of phenotypic, chemotaxonomic, DNA–DNA hybridization and phylogenetic analysis, it is proposed that these three strains represent a novel species, Marinobacter algicola sp. nov. The type strain is DG893 T (=DSM 16394 T =NCIMB 14009 T ). The genus Marinobacter was first proposed in 1992 to accommodate a novel Gram-negative, aerobic, halophilic gammaproteobacterium capable of degrading a variety of hydrocarbons (Gauthier et al., 1992). The type species, Marinobacter hydrocarbonoclasticus, was isolated from coastal waters, and since then a further 12 species of Marino- bacter have been recognized. These were isolated from various locations such as an offshore oil-well head (Huu et al., 1999), a coastal thermal spring (Shieh et al., 2003), temperate (Yoon et al., 2004) and Antarctic (Shivaji et al., 2005) sea water, saline soils (Martı´n et al., 2003) and marine sediments (Gorshkova et al., 2003; Romanenko et al., 2005). To date, only Marinobacter bryozoorum 50-11 T has an identifiable biological source, having been isolated from homogenized bryozoan tissue (Romanenko et al., 2005). The bacterial flora associated with the dinoflagellates Gymnodinium catenatum Graham and Alexandrium tamar- ense (Lebour) Balech have been proposed to be involved in producing a potent suite of neurotoxins, the paralytic shellfish toxins (PSTs), produced by these algae (Gallacher et al., 1997; Kodama et al., 1990). As a part of the work to understand the relationship between the bacterial flora of PST-producing dinoflagellates and PST production, we identified bacterial isolates with a phylogenetic affiliation to M. hydrocarbonoclasticus in laboratory cultures of these dinoflagellates that formed a discrete phylogenetic cluster (Green et al., 2004; Hold et al., 2001). The phylogenetic clustering and frequency of occurrence in laboratory cultures was suggestive of a specific association between the dino- flagellate and the M. hydrocarbonoclasticus-like isolates (Green et al., 2004; Hold et al., 2001). Bacterial isolates Abbreviation: PSTs, paralytic shellfish toxins. Published online ahead of print on 28 October 2005 as DOI 10.1099/ ijs.0.63447-0. The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains DG893 T , DG1136 and ATAM407-13 are AY258110, AY258116 and AJ294359, respectively. A transmission electron micrograph of cells of DG893 T and a table detailing the cellular fatty acid composition of the three novel strains and the type strains of other Marinobacter species are available as supplementary material in IJSEM Online. 63447 G 2006 IUMS Printed in Great Britain 523 International Journal of Systematic and Evolutionary Microbiology (2006), 56, 523–527 DOI 10.1099/ijs.0.63447-0