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Controls on microbial community structure in thermal environments : exploring bacterial diversity and the relative influence of geochemistry and geography

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/9315

Controls on microbial community structure in thermal environments : exploring bacterial diversity and the relative influence of geochemistry and geography

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Title: Controls on microbial community structure in thermal environments : exploring bacterial diversity and the relative influence of geochemistry and geography
Author: Mitchell, Kendra Renee
Advisor(s): Takacs-Vesbach, Cristina D.
Committee Member(s): Sinsabaugh, Robert L.
Northup, Diana E.
Crossey, Laura J.
Department: University of New Mexico. Biology Dept.
Subject: Microbial Ecology Yellowstone National Park
Biogeography
Energetic Modeling
Geochemistry
Microbial Ecology
Phylogenetics
LC Subject(s): Microbial ecology--Yellowstone National Park
Bacterial diversity--Yellowstone National Park
Hot spring ecology--Yellowstone National Park
Degree Level: Doctoral
Abstract: Community wide molecular surveys have revealed incredible hidden phylogenetic and metabolic diversity in microbial habitats. We have conducted the first microbial survey of Yellowstone National Park thermal environments, sampling 103 communities from across the park and across the range of conditions found. Yellowstone is particularly suited for this type of research because of the large number and wide variety of thermal springs, which are naturally occurring chemostats enabling examination of the factors that control microbes and drive community structure. In addition to samples for molecular microbial analysis, we collected water for extensive geochemical analysis in order to begin to deduce the microbes' role in situ. With this data we investigated patterns and correlations among the microbial communities, environmental geochemistry, and theoretical energy yield from 179 reactions that could be catalyzed by microbes. Prior to this work it was believed that temperature was the driver of microbial diversity in thermal communities, we have shown that pH is the most important factor controlling where communities are found. Through this extensive sequencing effort we have identified five major community types that can be described by the dominant organisms: Thermocrinis/Thermus, Phototrophs, Sulfurihydrogenibium, Hydrogenobaculum, and Proteobacteria/Bacteriodetes. The last group has never before been noted to be an important community type in thermal areas. The Proteobacteria/Bacteriodetes group is also interesting because it seems to thrive in the harshest conditions measured, low pH and high concentrations of metals. Additionally, sequences from 15 putative candidate phyla were recovered from multiple springs. The ecosystems described in this study are ideal for further application of ecological theory, especially community assembly patterns, biogeographic theory, and macroecological experiments that take advantage of the high diversity of habitats and short generation time of thermal communities. This work establishes a baseline of the communities inhabiting the range of thermal features in Yellowstone which will provide a foundation for future microbial research. The taxa-area relationship is regarded as one of the few laws in ecology. Although it has been investigated for decades in plants, animals, and insects; the taxa-area relationship has only begun to be examined in microbes. We evaluated the taxa-area and taxa-energy relationships in bacterial diversity of terrestrial hot spring "islands" representing the range of environmental conditions found in Yellowstone National Park. There was no significant relationship between species richness and either island size or energy available. Clone libraries of microbial communities under sample the diversity of those communities; therefore we also tested these relationships on estimated diversity. This study is the first to examine a large number of natural isolated microbial communities, but it is still possible that more extensive sampling is needed to detect the relationship between richness and island size. The work described here is unique in the number of microbial habitats studied, the intensity of the molecular sequencing effort, and the concurrent geochemical investigations. It is also the broadest application of thermodynamic energetic modeling done to date, which has enabled us to examine microbial communities across differing metabolic regimes as well as across geographic space. The combination of molecular and geochemical analysis of a wide variety microbial communities with energetic modeling of potential metabolisms forms a basis for future ecological studies of these environments.
Graduation Date: May 2009
URI: http://hdl.handle.net/1928/9315


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