Date of Award

Spring 2001

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)


Biological Sciences

First Advisor

Maki, James S.

Second Advisor

Courtright, James B.

Third Advisor

Noel, K. D.


Yellowstone Lake in Yellowstone National Park, Wyoming, is one of only a few freshwater systems recognized to contain active sublacustrine hydrothermal vents. The vents, situated throughout much of the lake's basin, emit reacted fluids rich in varied mineral nutrients and gases including hydrogen sulfide, methane and carbon dioxide. The temperature and chemical content of vent water 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 l6S rRNA gene cloning and sequencing approach was used to investigate the phylogenetic diversity of Archaea at three geographically- and geochemically contrasting Yellowstone Lake hydrothermal vents. Diverse and novel lineages of Archaea were present in the vent fluids. In general, 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 known to contain vigorous hydrothermal activity exhibited highest sequence similarity to Archaea earlier recovered from hot water environments, including marine hydrothermal vent systems and Yellowstone National Park terrestrial thermal springs. Clones from each vent tended to phylogenetically cluster, hinting chemistry and/or temperature of the vent fluids affected the development of Archaeal communities. Four clades represented by the clones appeared, to a large extent, unrelated to any heretofore-described Archaea. Interestingly, one of the clones generated during this study shared high sequence homology to env.pJP78, a clone previously produced from samples obtained from a terrestrial thermal spring in Yellowstone National Park. The clone appears to represent one of only a few known members of the early-diverged Korarchaea...



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