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Phylogenetic examinations of communities sampled along geochemical gradients provide a framework for inferring the relative importance of niche-based ecological interactions (competition, environmental filtering) and neutral-based evolutionary interactions in structuring biodiversity. Great Salt Lake (GSL) in Utah exhibits strong spatial gradients due to(More)
Subglacial sediments sampled from beneath Robertson Glacier (RG), Alberta, Canada, were shown to harbor diverse assemblages of potential nitrifiers, nitrate reducers, and diazotrophs, as assessed by amoA, narG, and nifH gene biomarker diversity. Although archaeal amoA genes were detected, they were less abundant and less diverse than bacterial amoA,(More)
Biological nitrogen fixation is a keystone process in many ecosystems, providing bioavailable forms of fixed nitrogen for members of the community. In the present study, degenerate primers targeting the nitrogenase iron protein-encoding gene (nifH) were designed and employed to investigate the physical and chemical parameters that underpin the distribution(More)
Improvements in purification of membrane-associated methane monooxygenase (pMMO) have resulted in preparations of pMMO with activities more representative of physiological rates: i.e., >130 nmol.min(-1).mg of protein(-1). Altered culture and assay conditions, optimization of the detergent/protein ratio, and simplification of the purification procedure were(More)
The Yellowstone caldera contains the most numerous and diverse geothermal systems on Earth, yielding an extensive array of unique high-temperature environments that host a variety of deeply-rooted and understudied Archaea, Bacteria and Eukarya. The combination of extreme temperature and chemical conditions encountered in geothermal environments often(More)
IMPORTANCE Leisure-time physical activity has been associated with lower risk of heart-disease and all-cause mortality, but its association with risk of cancer is not well understood. OBJECTIVE To determine the association of leisure-time physical activity with incidence of common types of cancer and whether associations vary by body size and/or smoking.(More)
Hydrogen (H₂) has an important role in the anaerobic degradation of organic carbon and is the basis for many syntrophic interactions that commonly occur in microbial communities. Little is known, however, with regard to the biotic and/or abiotic factors that control the distribution and phylogenetic diversity of organisms which produce H₂ in microbial(More)
Mounting evidence indicates the presence of a near complete biological nitrogen cycle in redox-stratified oceans during the late Archean to early Proterozoic (c. 2.5-2.0 Ga). It has been suggested that the iron (Fe)- or vanadium (V)-dependent nitrogenase rather than molybdenum (Mo)-dependent form was responsible for dinitrogen fixation during this time(More)
The [FeFe]- and [NiFe]-hydrogenases catalyze the formal interconversion between hydrogen and protons and electrons, possess characteristic non-protein ligands at their catalytic sites and thus share common mechanistic features. Despite the similarities between these two types of hydrogenases, they clearly have distinct evolutionary origins and likely(More)
Complex enzymes containing Fe-S clusters are ubiquitous in nature, where they are involved in a number of fundamental processes including carbon dioxide fixation, nitrogen fixation and hydrogen metabolism. Hydrogen metabolism is facilitated by the activity of three evolutionarily and structurally unrelated enzymes: the [NiFe]-hydrogenases,(More)