ROSEOBACTER-ALGICOLA SP-NOV, A NEW MARINE BACTERIUM ISOLATED FROM THEPHYCOSPHERE OF THE TOXIN-PRODUCING DINOFLAGELLATE PROROCENTRUM-LIMA

We describe a new species on the basis of phenotypic characteristics a nd the results of an analysis of small-subunit rRNA sequences. Three s trains of this organism were isolated from a culture of the toxin-prod ucing dinoflagellate Prorocentrum lima. These bacteria are gram-negati ve, strictly aerobic, ovoid organisms that are motile by means of one or two subpolar flagella. They grow at temperatures ranging from 10 to 37 degrees C and in the presence of NaCl concentrations ranging from 0.1 to 2 M and have an absolute requirement for sodium ions. They are strictly aerobic with a nonfermentative type of metabolism and are not able to grow anaerobically in presence or absence of nitrate. They do not denitrify. They exhibit oxidase, catalase, gelatinase, esculinase , beta-galactosidase, and (to a lesser extent) amylase activities. The three strains which we examined require thiamine and biotin for growt h. They grow only when glucose, trehalose, saccharose, fructose, malto se, pyruvate, malate, citrate, esculin, 2-ketoglutarate, 5-ketoglucona te, glutamate, or shikimate is present as a sole carbon source. The th ree strains have identical small-subunit rRNA sequences. A phylogeneti c analysis of these sequences revealed that these bacteria belong to t he alpha subdivision of the Proteobacteria and that they form a distin ct and robust monophyletic group with Roseobacter denitrificans and Ro seobacter litoralis. This result and the general phenotypic characteri stics of the organisms place them in the genus Roseobacter, although t hey do not produce bacteriochlorophyll alpha, in contrast to previousl y described Roseobacter species. On the basis of the phenotypic and ge netic similarities of these strains, we assigned them to a single spec ies, for which the name Roseobacter algicola is proposed. The type str ain is R. algicola FF3 (= ATCC 51440).