Browsing by Subject "Biogeochemistry"

Now showing 1 - 3 of 3
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    Developing a microfluidic device for in situ water column profiling of phototrophic sulfur bacteria
    (Office of the Vice Chancellor for Research, 2015-04-17) Kellogg, Austin; East, Zachary
    Phototrophic purple sulfur bacteria are crucial to study in Biogeochemistry because they are thought to be one of the first organisms to utilize photosynthesis. In the early atmosphere, there was very little oxygen present. Sulfur bacteria use light and sulfides as energy in anoxic conditions. Conditions suitable for sulfur bacteria can be found in anoxic lakes, which many are located in northern Indiana and the Pacific Northwest. The main goal of this project was to design and create a device that could record data and abstract samples of purple sulfur bacteria in anoxic lakes. In order to create this device, we first had to test the purple sulfur bacteria’s light absorbance using a spectrophotometer. The data collected about the sulfur bacteria’s absorbance was used by us to optimize our design for the circuit which incorporated the LED and Photo-detector components. Also, a Thermosensor component was added in an attempt to determine the optimal temperature sulfur bacteria lives in. Overall, six Op-amps were used in order to limit the amount of noise and to convert current into voltage so temperature and light absorbance can be measured.
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    Methane, arsenic, selenium and the origins of the DMSO reductase family
    (Nature Publishing group, 2020-07-02) Wells, Michael; Kanmanii, Narthana Jeganathar; Al Zadjali, Al Muatasim; Janecka, Jan E.; Basu, Partha; Oremland, Ronald S.; Stolz, John F.; Chemistry and Chemical Biology, School of Science
    Mononuclear molybdoenzymes of the dimethyl sulfoxide reductase (DMSOR) family catalyze a number of reactions essential to the carbon, nitrogen, sulfur, arsenic, and selenium biogeochemical cycles. These enzymes are also ancient, with many lineages likely predating the divergence of the last universal common ancestor into the Bacteria and Archaea domains. We have constructed rooted phylogenies for over 1,550 representatives of the DMSOR family using maximum likelihood methods to investigate the evolution of the arsenic biogeochemical cycle. The phylogenetic analysis provides compelling evidence that formylmethanofuran dehydrogenase B subunits, which catalyze the reduction of CO2 to formate during hydrogenotrophic methanogenesis, constitutes the most ancient lineage. Our analysis also provides robust support for selenocysteine as the ancestral ligand for the Mo/W atom. Finally, we demonstrate that anaerobic arsenite oxidase and respiratory arsenate reductase catalytic subunits represent a more ancient lineage of DMSORs compared to aerobic arsenite oxidase catalytic subunits, which evolved from the assimilatory nitrate reductase lineage. This provides substantial support for an active arsenic biogeochemical cycle on the anoxic Archean Earth. Our work emphasizes that the use of chalcophilic elements as substrates as well as the Mo/W ligand in DMSORs has indelibly shaped the diversification of these enzymes through deep time.
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    Nitrogen, Phosphorus and Carbon Dynamics during Storms in a Glaciated Third-Order Watershed in the US Midwest
    (2013-08-22) Johnstone, Joseph A.; Vidon, Philippe G.; Tedesco, Lenore P.; Licht, Kathy J.
    The characterization of the nutrients nitrogen, phosphorus and carbon (NPC) export to streams during storms is an integral part of understanding processes affecting water quality. Despite the fact that excessive levels of these nutrients in the Mississippi River basin adversely affects water quality in the Gulf of Mexico, little research has been conducted on NPC dynamics during storms on larger (>20 km2) agriculturally dominated Midwestern watersheds. This project examined the storm export of nitrate, ammonium, total phosphorus, and dissolved organic carbon (DOC) in the upper Eagle Creek Watershed (UECW) (274 km2) in Central Indiana, USA. Water samples were collected during five winter and spring storms in 2007 and 2008 on the rising and falling limb of the hydrograph, in order to characterize NPC dynamics during storm events. Stream discharge and precipitation was monitored continuously, and major cations were used to examine changes in source water over the duration of the storm and assist in the determination of potential flowpaths. DOC, total P, and TKN (Total Kjeldahl Nitrogen) tended to peak with discharge, while nitrate usually exhibited a slight lag and peaked on the receding limb. Total phosphorus, NH3-, TKN, and DOC appear to be delivered to the stream primarily by overland flow. NO3--N appear to be delivered by a combination of tile drain and macropore flow. Overall UECW displayed smoother nutrient export patterns than smaller previously studied watersheds in the area suggesting that scale may influence nutrient export dynamics. Further research is underway on a 3000 km2 watershed in the area to further examine the role scale may play in nutrient export patterns.