A numerical taxonomic study of Vibrio bacteria from a seasonally-cold ocean

Martin-Kearley, Jennifer (1992) A numerical taxonomic study of Vibrio bacteria from a seasonally-cold ocean. Masters thesis, Memorial University of Newfoundland.

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Abstract

Numerical analysis was used to characterize 113 Vibrio and five Aeromonas strains. The Vibrio were comprised of 33 type and reference strains, and 80 strains isolated from the seasonally-cold coastal waters of Newfoundland. The sources of the regional cold-ocean strains were brown alga and scallops. A property shared by all of the cold-ocean strains, and only some of the type and reference strains, was an ability to grow at 4°C. Several conditions, which might affect the outcome of the study, were investigated. Based on the results obtained it was decided to use, routinely, an incubation temperature of 20°C. Tests for growth on organic compounds as sole sources of carbon and energy were incubated for three weeks there than the more common six day period. The treatment of weak positive results as weak positive, positive, or negative was investigated also. It was decided that the general conclusions reached in the study would not be significantly altered by the interpretation of weak positive results. -- Strains were divided into two categories. These were made up of strains that tested positive for the arginine dihydrolase pathway and those that tested negative. All of the arginine dihydrolase-positive regional strains were from alga and most were identified as V. splendidus biovar I, a species of Vibrio known to grow at 4°C. One arginine dihydrolase-positive strain resembled V. diazotrophicus or V. aestuarianus. Of the arginine dihydrolase-negative strains, most of the strains that could be identified were designated V. marinus, although these strains also resembled the fish pathogen V. ordalii. The former is known to grow at 4°C and the latter is not. A small number of arginine dihydrolase-negative strains were identified as V. cyclosites and C. ordalii. Four clusters of regional strains could not be identified. These may represent new species or biovarieties. These strains, all of which grew at 4°C, clustered separately from some type strains, none of which grew at this temperature. It was concluded that some of the cold-ocean strains belonged to known species of Vibrio, mostly ones that can grow at cold-ocean temperatures. However, not all strains could be identified and further studies may show these to be new species or biovarieties of Vibrio.

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