Investigations on the microbial ecology of Yellowstone Lake hydrothermal vents
Abstract
Hydrothermal vents situated throughout Yellowstone Lake emit mineral nutrients that may profoundly influence the microbial ecology of the lake. This dissertation presents results from three main lines of inquiry. First, if nutrient composition and temperature of vent fluids influences the development of nearby microbial communities, then distinct communities of microbes should be detected at different vents. A 16S rRNA gene cloning and sequencing approach was used to investigate the phylogenetic diversity of Archaea at three geographically- and geochemically contrasting vents. Clones generated from DNA retrieved from a warm water hydrothermal vent showed rRNA gene sequence similarity to Archaea previously found in pedestrian environments, including agricultural soils and freshwater lake sediment. Clones recovered from vents in areas of the lake containing vigorous hydrothermal activity had high sequence similarity to Archaea earlier recovered from hot water environments, including marine hydrothermal vent systems and terrestrial thermal springs. One clone appears to represent one of only a few known members of the early-diverged Korarchaea . Second, if nutrient deprived, but metabolically poised, thiosulfate-oxidizing bacteria are plentiful in Yellowstone Lake bulk water, then chemoautotrophy in bulk water should be stimulated by thiosulfate. The results show that at the sites sampled during this study, vigorous chemoautotrophic activity was limited to hydrothermal vent fluids. Chemoautotrophy was not stimulated by thiosulfate, therefore thiosulfate-oxidizing bacteria may not have been abundant in bulk lake water. Third, if hydrothermal vent fluids support the growth of a range of metabolic types, including chemoautotrophic and chemoorganotrophic bacteria, then large numbers of these bacteria should be found in vent fluids. The number of cultivable chemoorganotrophic bacteria was significantly higher in vent fluids as compared to bulk water. A representative of the most numerous (as estimated by MPN analysis) chemoorganotrophic bacterium was isolated in pure culture and characterized. The data suggest Yellowstone Lake hydrothermal vent water is home to various microorganisms, including (i) a diversity of Archaea , (ii) metabolically active chemoautotrophic bacteria, and (iii) metabolically active chemoorganotrophic bacteria.
This paper has been withdrawn.