A group of phenotypically similar bacteria were isolated from estuarine waters and shellfish from the Oregon coast by procedures designed for the isolation of potentially pathogenic Vibrio species. Although these strains were typical of bacteria of the genus Vibrio, they could be distinguished from previously described species by their arginine di hydrolase activities, negative Voges-Proskauer reactions, fermentation of sucrose and lactose, and inability to grow in 0 or >5% added NaCl. The deoxyribonucleic acid base compositions of these strains ranged from 43 to 44 mol% guanine plus cytosine. There was >85% deoxyribonucleic acid relatedness among these strains (melting temperature -15°C; membrane filter competition method), whereas there was <25% relatedness with other Vibrio species, including Vibria anguillarum, Vibrio nereis, and Vibrio splendidus, which are also arginine dihydrolase positive and have similar guanine-pluscytosine contents. Our results indicate that the strains which we studied are distinct from previously described species of the genus Vibrio, and we propose the name Vibrio aestuarianus for these strains, indicating their estuarine origin. The type strain is strain OY-0-002 (= ATCC 35048).The recent realization that Vibrio species pathogenic to humans were endemic to United States coastal waters has led to a renaissance in the study of the ecology, pathogenicity, and taxonomy of these bacteria. This renewed effort has led to the recent reorganization of the genus Vibrio (2) and to descriptions of a number of new species (3-5, 7, 8, 10).During the course of a survey to determine the distribution of pathogenic Vibrio spp. in estuarine waters and shellfish from the coast of Oregon (D. L. Tison, M. Nishibuchi, and R. J. Seidler, Abstr. Annu. Meet. Am. SOC. Microbi-01. 1981, Q97, p. 216), phenotypically similar bacteria which were distinct from previously described Vibrio species were isolated. Comparisons with other lactose-fermenting Vibrio species indicated that the arginine dihydrolase-positive, lactose-positive strains isolated from Oregon estuaries were probably a new Vibrio species (11).In this paper we describe the characteristics of these strains and show that these bacteria were genetically distinct from other phenotypically similar Vibrio species, thereby warranting their designation as a new species, Vibrio aestuarianus
MATERIALS AND METHODSBacterial strains. Strains from water and shellfish from the Oregon coast were isolated by inoculating alkaline peptone broth and subsequently plating and isolating the organisms on thiosulfate-citrate-bile saltssucrose agar (Oxoid) (6). The sources of V . aestuarianus and the reference strains used in this study are listed in Table 1.Phenotypic and genetic characterization. The media and methods used in phenotypic characterizations, deoxyribonucleic acid (DNA) base composition determinations, and DNA-DNA hybridization studies were essentially as described previously (12, 13).
RESULTS AND DISCUSSIONVibrio aestuarianus sp. nov. The type strain of V...