Five strains isolated from mussels (harvested off the Atlantic Spanish coast in 1985 and 1986) were found to be phenotypically distinct from previously described Vibrio species, They showed 94 to 100% intragroup relatedness as determined by DNA-DNA hybridization (S1 nuclease method) but were found to be only 1 to 25% related to other Vibrio species. These strains have all of the properties that define the genus Vibrio and can be clearly differentiated from other species by their positive responses in tests for Thornley's arginine dihydrolase, gas production from glucose, growth in media containing 10% NaCl, and acid production from sucrose, L-arabinose, D-xylose, and D-cellobiose and their negative responses in tests for lysine decarboxylase, the Voges-Proskauer reaction, growth without NaCl and at 40°C, hydrolysis of gelatin, casein, starch, DNA, and alginate, and acid production from D-mannose. The G+C ratio of the DNA is 45 to 46 mol%. The name Vibriu mytili is proposed for the new species; strain 165 (= CECT 632) is the type strain.The genus Ebrio currently contains more than 35 species, most of which are of marine origin. In addition to the 22 Vibrio species described in Bergey's Manual of Systematic Bacteriology (2), 14 new species have been recognized (3,4, 7, 9,15,17,18,20,24,31,33,36,37,41)-Phenotypic characterization data for many fresh isolates indicate that it is often difficult to correctly identify these organisms to species level and suggest that a number of isolates might correspond to undescribed species (6,21,28,39,40).It is generally agreed that a bacterial species is a group of strains with high levels of intragroup DNA relatedness which can also be recognized by phenotypic traits (38). There is no such operational definition of a genus at the present time. Although phylogenetic criteria are of tremendous importance in delineating a genus (and higher taxa), it has been agreed that genera should contain species with common phenotypic traits to allow phenotypic identification at the genus level (26). Although splitting of the genus Vibrio into Hbrio sensu strict0 and the genus Listonella on the basis of molecular data has been proposed (25), there is not general agreement about the constituent species of the genus Listonella (10,35) or the phylogenetic justification of this proposed genus (8,27), and most workers still refer to Listonella spp. as Ebrio spp. for phenotypic reasons.Five strains isolated from mussels could not be identified as any known Vibrio species (28). The purpose of this work was to examine the taxonomic position of these strains relative to known species by DNA-DNA hybridization and extensive phenotypic tests. The outcome is the description of a new species named Vibrio mytili.
MATERIALS AND METHODSBacterial strains. I? mytili 163, 165= (T = type strain), 167, 178, and 185, the strains that constituted phenon 3 (28), were isolated from Mytilus edulis and were maintained as working stocks at room temperature in semisolid seawater agar containing 1% (wt/vol) peptone, 0.3% mea...
