First Advisor

Anna-Louise Reysenbach

Date of Publication


Document Type


Degree Name

Doctor of Philosophy (Ph.D.) in Biology






Submarine geology, Marine microbial ecology, Hydrothermal vent ecology, Microorganisms



Physical Description

1 online resource (xv, 178 p.) : ill. (some col.)


The discovery of deep-sea hydrothermal vents in 1977 revealed an ecosystem supported by chemosynthesis with a rich diversity of invertebrates, Archaea and Bacteria. While the invertebrate vent communities are largely composed of endemic species and exist in different biogeographical provinces, the possible factors influencing the distribution patterns of free-living Archaea and Bacteria are still being explored. In particular, how differences in the geologic setting of vent fields influence microbial communities and populations associated with active vent deposits remains largely unknown. The overall goal of the studies presented in this dissertation was to examine the links between the geologic setting of hydrothermal vent fields and microorganisms associated with actively venting mineral deposits at two levels of biological organization. At the community level, bar-coded pyrosequencing of a segment of the archaeal and bacterial 16S rRNA gene was employed to characterize and compare the microbial communities associated with numerous deposits from several geochemically different vent fields. Results from these studies suggest that factors influencing end-member fluid chemistry, such as host-rock composition and degassing of magmatic volatiles, help to structure the microbial communities at the vent field scale. At the population level, targeted cultivation-dependent and -independent studies were conducted in order to expand our understanding of thermoacidophily in diverse hydrothermal environments. Results of these studies expanded the phylogenetic and physiological diversity of thermoacidophiles in deep-sea vent environments and provided clues to factors that are influencing the biogeography of an important thermoacidophilic archaeal lineage. Overall, these studies have increased our understanding of the interplay between geologic processes and microorganisms in deep-sea hydrothermal environments.


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Portland State University. Dept. of Biology

Persistent Identifier