Numerical taxonomy of Vibrionaceae from Newfoundland coastal waters

Numerical analysis was used to characterize 111 Vibrionaceae strains. These included 31 reference cultures belonging to the genera Aeromonas, Listonella, and Vibrio and 80 strains isolated from the seasonally cold coastal waters of Newfoundland. The sources of the regional strains were the brown alga Alaria esculenta and the giant scallop Placopecten magellanicus. Most of the regional strains grew at temperatures associated with psychrotrophs, while a small proportion may have been psychrophilic. All of the regional strains grew at 4 °C. A routine incubation temperature of 20 °C was chosen and in tests for utilization of organic components as sole sources of carbon and energy the strains were incubated for 3 weeks rather than the more common 6-day period. The treatment of weak positive results as weak positive, positive, or negative was investigated and it was decided that the general conclusions reached in the study would not be significantly altered by the interpretation of weak positive results. Using numerical analysis it was shown that most of the strains clustered according to source. Most reference cultures were more closely related to each other than they were to the regional strains. Some strains were phenotypically similar to Vibrio splendidus biovar I, which is arginine dihydrolase positive. Although there were differences, some strains were similar to the fish pathogen Vibrio ordalii, which is negative for arginine dihydrolase. Both species are reported to grow at 4 °C. It was shown that most of the regional Vibrionaceae strains studied were different from previously described species belonging to the family Vibrionaceae.Key words: numerical taxonomy, Vibrionaceae, Vibrio, marine bacteria, psychrotroph.