Characterization of bacteria from the sediment-water interface of Newfoundland coastal waters using patterns of carbon source utilization

Goudie, E. Dwayne (1997) Characterization of bacteria from the sediment-water interface of Newfoundland coastal waters using patterns of carbon source utilization. Masters thesis, Memorial University of Newfoundland.

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Abstract

The functional diversity of marine bacteria from the sediment-water interface of Newfoundland coastal waters was characterized by examining carbon source utilization. Although some benthic strains utilized a broad range of substrates, many were considered fastidious. Bacteria with a strictly respiratory metabolism predominated at the sediment water interface. Upon initial isolation, approximately 50% of the colonies observed on the plating medium, at 15°C, were pigmented. Most studies do not report a significant proportion of pigmented bacteria occurring in the marine environment. The proportion of pigmented bacteria was much lower if the plates were incubated at 5°C. The recovery of bacteria was higher at 15°C, than at 5°C, therefore the population studied was psychrotrophic rather than psychrophilic. Eighty percent of the strains isolated required Na for growth, indicating that the population studied was mostly of marine origin. The Biolog-GN assay showed that strains were more metabolically active in September than in June. There was no functional difference in the substrates utilized by strains at each sampling date, isolation temperature, or between groups of pigmented and non-pigmented bacteria. Sixty-six percent of all cultured strains utilized glucose and 62% utilized glutamic acid. These were among the most widely utilized substrates on the Biolog microplate. They may, therefore, be the most appropriate choices as substrates for studies of heterotrophic potential as long as the percentage of the population actually metabolizing them is considered. Approximately 38% of the strains, subdivided as 17% of the pigmented strains and 54% of the non-pigmented strains, utilized thymidine and 20% utilized leucine. These compounds can be used to estimate bacterial growth rates assuming that they are incorporated directly into DNA or proteins, respectively. If the bacteria metabolize these compounds as substrates their use in estimating microbial growth rates could result in an underestimation of the true microbial production occurring in this region, especially if non-pigmented bacteria are abundant. Based on the results of Biolog substrate utilization patterns there were significant differences between the regional strains and most of the reference cultures with the reference strains being more metabolically active and utilizing a broader range of substrates.

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