Browsing by Subject "Integrated biosciences"
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Item Avian communities of managed and unmanaged boreal forests.(2012-04) Zlonis, Edmund JosephI compared the breeding bird communities of managed and unmanaged boreal forests in northeastern Minnesota. Birds were sampled in the spring and summer of 2010 and 2011 in the Superior National Forest (SNF, managed landscape) and Boundary Waters Canoe Area Wilderness (BWCAW, unmanaged landscape). Twelve point counts were completed along each of 10 paired transects for a total of 240 points, 120 points within each of the SNF and BWCAW. The total number of individuals detected per point was significantly higher within the BWCAW (F=9.76, p=0.01). Avian species richness per point was also significantly higher within the BWCAW (F=11.17, p<0.01). These results were negatively correlated with increased amounts of regenerating forests (mainly from logging) and positively correlated with tree species richness and canopy height of forest stands. Eight species were more common in the BWCAW compared with the SNF (black-capped chickadee (Poecile atricapillus), brown creeper (Certhia americana), Canada warbler (Cardellina canadensis), golden-crowned kinglet (Regulus satrapa), least flycatcher (Empidonax minimus), red-breasted nuthatch (Sitta canadensis), winter wren (Troglodytes hiemalis), and yellow-bellied flycatcher (Empidonax flaviventris)). Only the mourning warbler (Geothlypis philadelphia) and chipping Sparrow (Spizella passerina) were more common in the SNF. Species associated with mature or mixed forests tended to be found in the BWCAW at higher densities. In general, most species associated with early successional habitats did not differ between the BWCA and SNF landscapes. Results suggest that northern Minnesota forests with natural successional and disturbance regimes provide habitat for a higher density and richness of bird species.Item Characterization of glycosylphoshatidylinositol-anchored ceruloplasmin in multiple redent organs following dietary copper deficiency.(2010-10) Mostad, Elise JuneCopper is a necessary metal cofactor in many enzymes that catalyze key reactions in both prokaryotes and eukaryotes. Ceruloplasmin (Cp) is a copper-dependent enzyme that acts as a ferroxidase, oxidizing FeII to FeIII for systemic iron mobilization. Cp is expressed as both a secreted plasma (sCp) enzyme and a membrane-bound glycosylphosphatidylinositol- anchored (GPI-Cp) splice variant enzyme. sCp is the most abundant copper-binding protein in mammalian plasma. The ferroxidase activity of Cp is essential for iron mobilization, as Cp null humans and mice exhibit selective tissue-specific iron overload. Dietary copper deficient (CuD) rodents have near total loss of Cp activity, severe loss of Cp protein, and anemia. The impacts of dietary copper deficiency on GPICp has not been previously evaluated. Studies were conducted in Holtzman and Sprague- Dawley rats, albino mice, and Cp -/- mice, to investigate the copper-iron interaction and further characterize GPI-Cp. Purified membrane extracts of these rodent tissues detected immunoreactive Cp protein, especially enriched in spleen and kidney, but not in membranes from Cp -/- mice. Immunoreactive Cp protein was released with phosphotidylinositol-specific phospholipase C treatment and released protein exhibited ferroxidase activity. These data suggest that the membrane-bound Cp immunoreactivity detected is GPI-anchored. Following perinatal and postnatal copper restriction, GPI-Cp was markedly lower in spleen and modestly lower in liver of CuD rats and mice, compared to copper-adequate (CuA) rodents. Livers of CuD mice contained elevated liver non-heme iron (NHI), while spleen NHI was lower in CuD than CuA rats, and not different in CuD mice, implying that lower GPI-Cp was not correlated with augmented NHI levels in CuD rodent spleens. Spleen and liver membranes of CuD rats expressed augmented levels of ferroportin, the iron efflux transporter, which may compensate for the loss of GPI-Cp in iron efflux. Copper deficient rats and mice both develop severe anemia but only in rats is plasma iron lower than normal, consistent with impaired Cp function. As multicopper oxidases like Cp are thought to be the major metabolic link between copper and iron, additional research is needed to determine the impact, if any, of lower GPI-Cp on iron flux and the development of anemia when copper is limiting.Item The effect of catchment urbanization on nutrient uptake and biofilm eneyme activity in Lake Superior (USA) tributary streams.(2011-08) Lehto, LaRae Lea PetersonSummary abstract not availableItem The effect of urbanization on the stopover ecology of neotropical migrant songbirds(2015-04) Condon, Elisabeth LeeI conducted spring migration point counts and vegetation surveys at 29 forest patches in the Chicago, IL metropolitan area in 2012 and 2013. The forest patch selection was designed to test the effects of patch size, distance from the Lake Michigan shoreline and degree of urbanization. I conducted exploratory analysis to search for potential relationships. Vegetation structure variables, especially understory and subcanopy composition, were important factors for many models. Bird species determined to be area sensitive in previous studies were associated with large patches during migration. While path size, distance from the shoreline and urbanization were not frequently selected for models of the entire avian community, they were important in most models of individual species. No single combination benefitted all species, indicating that maintaining a variety of conditions in the region will support a diverse avifauna.Item Effects of external and internal nutrient supplies on decomposition of wild rice, Zizania palustris.(2011-02) Hildebrandt, Lauren R.How external and internal nutrient supplies affects wild rice shoot and root litter decomposition and the nitrogen (N) and phosphorus (P) dynamics in decaying litter were examined in two experiments. In a site quality experiment, wild rice shoot and root litterbags were decayed in mesocosms in the field with added N or P or a control as ambient conditions, over 115 days. In the second litter quality experiment, wild rice plants were grown with N, P, both, or none, to produce litter of different qualities and then decayed for 168 days under controlled temperature in the laboratory. The impacts of both site and litter quality was greater on shoot litter than root litter. In the site quality experiment, P addition significantly increased wild rice shoot decay more than N addition and reduced P mineralization over time compared to the control. Neither adding N nor P influenced root decay, but adding P increased root P immobilization compared to the control, and the effect was much greater in root litter compared to shoot litter. In the litter quality experiment, P enrichment increased litter quality by increasing P concentrations and water-soluble compound concentrations in shoot litter and decreasing lignin concentrations in root litter, thereby increasing decay rates of both shoot and roots, although, the impact was much greater on shoot decay. N enrichment increased plant growth but reduced shoot litter quality and decay likely because these larger plants had greater lignin concentrations for structural support and lower phosphorus concentrations and lower N:P ratios. Increased lignin likely overrides a concomitant increase in nitrogen concentration in shoot litter and appears to control wild rice decomposition. Initial lignin:P,C:P, lignin+asid-solubles:P and the N:P ratios of shoot litter were correlated to the final mass remaining. Lignin and phosphorus appear to play a key role in driving wild rice decay through the opposite effects that each have on litter quality.Item Effects of nanosilver on Daphnia magna and pimephales promelas.(2010-08) Hoheisel, Sarah M.The increasing use of nanosilver in consumer products and the likelihood of environmental exposure warrant investigation into the toxicity of nanosilver to aquatic organisms. A series of studies were conducted comparing the potency of nanosilver to ionic silver (Ag+) at acute and sublethal levels. The results of these tests were examined for evidence that nanosilver acts by a different mechanism of toxicity than Ag+, with the goal of estimating the adequacy of current water quality regulations based on the toxicity of Ag+ to protect against environmental effects of nanosilver. A variety of simple methods to separate Ag+ from nanosilver by physical exclusion or charge selectivity were assessed in preliminary studies for the ability to provide insight into the mechanism of nanosilver toxicity. In a definitive study, ion exchange resin was used to remove Ag+ from nanosilver (confirmed by the complete removal of silver from AgNO3 solutions) in order to determine the importance of Ag+ to acute toxicity of nanosilver to Daphnia magna. The acute toxicity of nanosilver to D. magna after ion exchange was shown to be similar to that of untreated nanosilver, suggesting that Ag+ did not contribute significantly to the toxicity of the suspensions, or that ion release occurred rapidly after ion exchange. D. magna juveniles were exposed to four sizes of nanosilver (10, 20, 30 and 50 nm) and Ag+ and 48-h LC50s were calculated for each material. Based on mass concentrations, all nanosilver sizes were less acutely toxic than Ag+, and a trend of increasing toxicity with decreasing average diameter of nanosilver was observed, with LC50s ranging from 19-42 times higher than that of Ag+. Calculations of nanosilver specific surface area and theoretical surface atoms revealed little to no difference in LC50s among the four sizes, suggesting that toxicity may be dependent on the surface properties of nanosilver. Equivalent calculations for an ionic Ag exposure series resulted in the finding that, in terms of total surface Ag atoms, all sizes of nanosilver were more acutely toxic than equivalent exposures of pure Ag+. This implies either that a second mechanism of toxicity exists for nanosilver which increases its overall potency, or that the calculation of surface atoms was an underestimate due to the continuous release of Ag+ from nanosilver into the matrix. Acute-to-chronic ratios (ACRs) were obtained for Pimephales promelas (<24 hours post hatch) exposed to both Ag+ and nanosilver, to test the hypothesis that a difference in these ratios would indicate different mechanisms of toxicity. The results of 96-h acute and 7-day sublethal toxicity tests produced ACRs for Ag+ and nanosilver that were not significantly different based on their overlapping confidence intervals. Furthermore, the observation that the nanosilver ACR was smaller than that of Ag+, suggest that if there is a separate toxicity mechanism in nanosilver, it is unlikely to result in environmental effects beyond those that would be expected from an Ag+ exposure. Further studies are needed to determine the degree to which the results of the ion exchange and size-dependent toxicity tests can be attributed to nanosilver dissolution. Overall, the results of these tests do not provide unambiguous evidence for a mechanism of nanosilver toxicity other than Ag+. The U.S. EPA maximum allowable silver concentration for natural waters is based on dissolved silver, defined as that which passes through a 0.45 μm filter, which is considerably larger than the average size of nanosilver aggregates in the exposure media. Therefore, the presence of nanosilver in the environment will increase the apparent dissolved Ag concentration, resulting in increased protectiveness of this criterion.Item Evaluation of erythrocyte copper chaperone for superoxide dismutase (CCS) as a biomarker for marginal copper deficiency.(2011-12) Lassi, Katie ChristinaCopper is an essential dietary trace metal responsible for the functioning of at least 12 mammalian enzymes. Despite current increases in cases of copper deficient humans, a sensitive, reliable, and easily evaluated copper deficiency biomarker has yet to be identified. Multiple studies using rodent models were used to evaluate currently accepted blood biomarker proteins through Western blotting and activity assays. In the first study, male postweanling Sprague Dawley rats were fed copper deficient (CuD) or copper adequate (CuA) diets and deionized water and sampled after one, two, and four weeks. A group fed an iron deficient diet (FeD) was also included and sampled after two weeks. Lastly, after the four weeks a repletion study was performed for two weeks with samples taken after a total of six weeks of study. Superoxide dismutase (Sod1) and ceruloplasmin (Cp) were influenced by CuD and FeD diets, while the copper chaperone for superoxide dismutase (CCS) and the ratio of CCS/Sod1 were influenced only by CuD diet and after just one week. Blood cuproenzymes from CuD repleted rats normalized after two weeks on the CuA diet. Next, for two weeks male postweanling Sprague Dawley rats were fed CuA or CuD diets and compared with a group of marginally copper deficient (CuM) rats whose water was copper supplemented. Although differences between the CuD and CuM groups versus the CuA groups were identified, only CCS showed statistically different results between all groups, allowing for the identification of marginally copper deficient individuals. Further, there was high negative statistical correlation between liver copper and erythrocyte CCS. For all mouse trials, Swiss Webster mice were fed either CuD or CuA diets for five weeks. In one experiment, postweanling mice were housed in solid bottom cages and thus had access to their feces. In another postweanling mice were housed in stainless steal mesh bottom cages. CuD mice from solid bottom cages were found to be less deficient, likely due to coprophagia. These animals showed no reduction in plasma Cp or Sod1 expression, but did have higher CCS expression. Lastly, adult Swiss Webster mice were house in stainless steal mesh bottom cages and then evaluated for copper deficiency. CuD adult mice had no changes in Cp activity, liver copper levels, hemoglobin quantities, or Sod1 and Cp expression, but they did have a significantly elevated expression of CCS. These rodent model results indicated that CCS maybe an excellent biomarker for marginal copper deficiency in human diagnosis due to CCS’s reliability and sensitivity to variable copper status.Item Foraging mechanisms of siscowet Lake Trout (Salvelinus namaycush siscowet) on pelagic prey(2014-12) Keyler, Trevor DanielLittle is known about the foraging mechanisms of siscowet (Salvelinus namaycush siscowet), the most abundant piscivore within Lake Superior because they occupy light-limited environments as a result of diel vertical migration. The reaction distance, angle of attack, and foraging success were determined for siscowet during laboratory trials under lighting conditions that approximated downwelling spectral irradiance and intensity (0-10 lx) at daytime depths. Siscowet reaction distance in response to golden shiners (Notemigonus crysoleucas) was directly correlated with increasing light intensity until saturation at 0.01 lx, and afterwards the relationship was asymptotic within our range of tested light intensities. In total darkness, lateral line sensory detection was sufficient to locate prey at 24.9 ± 1.7 cm, while increasing light intensities increased reaction distance up to 58.6 ± 2.3 cm at 10 lx. Larger prey elicited higher reaction distances than smaller prey at all light intensities while moving prey elicited higher reaction distances than stationary prey at the higher light intensities (0.001-10 lx). The capture and consumption of prey similarly increased with increasing light intensity while time to capture decreased with increasing light intensity. The majority of orientations toward prey occurred within 120° of the longitudinal axis of the siscowet's eyes, although reaction distances among 30° increments along the axis were not significantly different. Our predictive model will help determine reaction distances for siscowet in various photic environments and will help identify the mechanisms and behavior that allow for low light intensity foraging within freshwater systems.t>Item A Geographic Mosaic of Speciation in Eurosta solidaginis(2012-07) Lindberg-Livingston, Annelie JoyEcological speciation occurs when divergent selection in different habitats creates strong selection for reproductive isolation which counteracts the homogenizing effects of gene flow between populations using those different habitats. Multiple divergent selection pressures can affect isolation and the strength of these selection pressures can vary geographically. Sympatric pairs of populations using different habitats in separate geographic areas may experience varying degrees of diversifying selection. Differing degrees of reproduction isolation between the populations result in what may be called a “Geographic Mosaic of Speciation”. A Geographic Mosaic of Speciation provides an opportunity to study the process of speciation in various degrees of completion. Eurosta solidaginis (Diptera: Tephritidae) is a fly that induces galls on tall goldenrod (Solidago altissima; Compositae) in North America with populations in the forest and prairie biomes of Minnesota, which are under divergent ecologically-based selection pressures. Previous research indicates that the goldenrod, the gallfly, and the natural enemies of the gallfly in the prairie and the forest biomes are genetically differentiated. I measured characteristics of each member of this three-trophic-level interaction across the prairie-forest biome border in order to characterize divergent selection on members of this interaction. I found that differences in the host plants, flies, and their natural enemies were distributed in a geographic mosaic at the prairie-forest biome border. Some neighboring populations were highly differentiated in a range of characteristics while others showed less differentiation. I then tested two pairs of neighboring fly populations to measure their degree of reproductive isolation and their adaptation to host-plants. The goldenrods from these paired sites were morphologically differentiated from each other. Flies from three out of the four sites tested had higher survival on plants from their own site than plants from the neighboring site, which shows that differences in plant morphology are correlated with differential selection of host-plants on E. solidaginis flies. Reproductive isolating mechanisms of the flies across the boundary are also distributed in a geographic mosaic which supports our hypothesis that these flies show a Geographic Mosaic of Speciation.Item The habitat of winter ticks (Dermacentor albipictus) in the moose (Alces alces) range of Northeast Minnesota(2015-03) Terry, JuliannWinter ticks occur throughout moose range south of 60º N, but little is known about how habitat influences tick density in Minnesota. Adult female winter ticks drop off moose in the spring to lay eggs and larvae attach to moose in the fall. The habitat that a tick drops off into could increase or decrease either survival or reproduction. Moose select different cover types for foraging and for bedding. We used locations of moose wearing GPS collars to identify tick sampling locations. Moose GPS locations could be identified as either movement or bedding. Targeted sampling at moose GPS locations allowed us to evaluate flag and walking surveys for winter tick collection. Bed sites and movement paths were identified from the 2013 and 2014 spring tracks to assess the effect of moose behavior and habitat characteristics on tick density. Moose GPS locations had more ticks than random sites (p = 0.001). Tick densities at moose sites were higher in 2013 (10.8 ± 2.9 ticks/m2) than in 2014 (2.8 ± 1.2 ticks/m2; p=0.0003). Ticks were found at 52% of 2013 sites and at 27% of 2014 sites. More movement paths than bed sites had ticks in 2013 (p = 0.01), but tick densities were similar in bed sites (11.2 ± 6.3 ticks/m2) and movement paths (10.7 ± 7.5 ticks/m2). In both years, tick density was higher in areas with litter depths < 3 cm (p < 0.06) and with canopy closures < 50% (p < 0.008). A high percentage of sites in lowland conifer, mixedwood, and regenerating forests had ticks present, but no upland conifer sites had ticks present (p = 0.0001). Spring locations from GPS collared moose were converted to paths. These paths were areas where ticks would have dropped off of moose. We created paths of moose in the fall by connecting GPS locations. Fall paths were overlaid with spring movement paths to identify areas where moose could acquire ticks. Overlaps of the 2011-2012 spring and fall path accounted for 6 and 13% (3.1 ± 0.4 ha and 2.2 ± 0.5 ha) of the paths. All moose overlapped with their own path in the fall for about 4% of their spring paths (1.1 ha). The greatest areas of overlap occurred in mixedwood and wet cover types (p = 0.0002). Mixedwood and wet cover types, especially with open canopies and shallow litter depths, have the highest potential to produce high larval tick densities. Mixedwood and wet cover types also have the greatest area of overlap between spring and fall paths and could be the areas with the highest tick transfer.Tick densities estimated from walking surveys and tick densities estimated from flag surveys were similar (p=0.9). Walking surveys with chaps allowed us to identify the height of winter ticks on the vegetation. The largest clumps of ticks were found at 38.2 ± 3.4 cm, but ticks were found from 0-100 cm. When more ticks were collected with walking surveys, ticks were generally found below 66 cm. When more ticks were collected with flag surveys, ticks were found above 66 cm and were likely higher than chap height.Item The influence of lake and stream conditions on survival of migratory rainbow trout in the Bois Brule (Wisconsin) and Knife (Minnesota) rivers.(2012-07) Kaspar, Tyler JosephRainbow trout (Oncorhynchus mykiss) were introduced to the Laurentian Great Lakes from the Pacific Coast and make up an important part of the sport fishery. The potamodromous life history variant (migratory rainbows or steelhead) is most prevalent among wild populations in the Great Lakes, where they hatch in-stream, migrate to the lake as juveniles, and return to the stream as adults to spawn. Large inter-annual variability in survival of steelhead populations from the Bois Brule River, WI, and Knife River, MN, in western Lake Superior has been observed, but the underlying mechanisms have not been well explained. The focus of my study was to identify the underlying mechanisms that influence variability in survival of wild maiden spawning adults. Multiple linear regression analyses were used to identify in-stream and in-lake (western Lake Superior) sources of variability, and to indicate the environment (stream or lake) that was most limiting. Data for wild maiden spawning rainbow trout, including abundance, stream age and lake age, were provided by the WI and MN Departments of Natural Resources. The in-stream analyses included stream temperature, flow, precipitation, and winter minimum air temperature. The lake analyses included surface temperature, lake trout (Salvelinus namaycush) (predator) abundance and forage abundance. For in-stream influences, I found that total September precipitation was negatively correlated with survival during the first stream year for Brule River steelhead. Total winter precipitation was positively correlated with survival of Knife River juveniles in their first stream year. However, first year survival of juvenile steelhead in the Knife River was negatively correlated with high stream temperatures (degree days > 20°C). The number of Brule River first returning steelhead (maiden returns) was positively correlated with surface temperature in western Lake Superior in their first lake year. Maiden returns of Knife River steelhead were negatively correlated with cisco density (kg/ha) in their second lake year. Overall, my results suggest that variability in maiden returning steelhead for both populations is better explained by conditions in their river of origin than conditions in western Lake Superior, which have a secondary influence and may better explain variability in repeat spawning and stocked steelhead.Item Isolation and characterization of novel mycobacteria species from Sarracenia purpurea(2015-03) Tran, Minh Phuong ThiSeveral fast to intermediate growing acid-fast, scrotochromogenic bacteria were isolated from Sarracenia purpurea pitcher waters in Minnesota sphagnum peat bogs. The isolates were identified by a polyphasic approach using morphological, biochemical, and bioinformatic techniques. Phylogenetic studies indicate the strains are located in the Mycobacterium genus with no obvious relation to any characterized type strains of mycobacteria. Two distinct clades emerged among the pitcher plant isolates, therefore two type strains (DL734 and DL739) were designated to represent the two clades. Phenotypic characterization revealed neither strain is similar to known genus type strains in collective properties of growth, pigmentation, or enzyme synthesis. Fatty acid methyl ester (FAME) profiles were unique for each type strain. The two isolates showed the unique ability to survive temperatures as low as 8°C. DL734 appeared to enter a viable but non-culturable state while DL739 appeared to be psychrotolerant. This could indicate that mycobacteria are more plastic in their ability to withstand different abiotic factors than previously recognized. The names Mycobacterium purpureae sp. nov. and Mycobacterium helvus sp. nov. are proposed for type strains DL734 (=JSM 30395 =NCCB 100519T) and DL739 (=JSM 30396=NCCB 100520T), respectively.Item Light, nitrogen and phosphorus effects on growth, allocation of biomass and nutrients, reproduction and fitness in wild rice (Zizania palustris L.)(2011-06) Sims, Lee T.Abstract summary not availableItem Localization of natriuretic peptide receptor A in the cochlea(2014-08) Prince, Sara CatherineNatriuretic peptides have been shown to alter fluid balance and ion levels in many tissues throughout the body including the renal and cardiovascular systems. When atrial natriuretic peptide (ANP) binds to its receptor (NPR-A), a dimerization event causes the activation of cGMP, initiating an internal second messenger cascade. Infusion of ANP causes improved hearing thresholds, theoretically stimulated by the secondary messengers initiated by the ANP pathway. The specific location of a natriuretic peptide receptor, NPR-A, in the inner ear including the exact mechanisms of the pathway stimulated by ANP binding, is still largely unknown.This study was designed to test the hypothesis that (1) NPR-A is in the cells of the cochlea critical for the regulation of endolymph and ion balance and (2) NPR-A is co-localized with the effector protein NKCC1, known for its role in the movement of potassium and other ions in the inner ear. Immunohistochemistry was performed on cryosections of cochlea collected from mice of normal hearing. Quantitative reverse-transcriptase polymerase chain reaction was also performed on kidney and cochlea homogenates, as well as laser capture microdissected cells to determine the mRNA levels of NPR-A in specific tissues.NPR-A was localized to six cell types in the cochlea including marginal and basal cells of the stria vascularis, root cells of the spiral ligament, interdental cells and limbal fibrocytes of the spiral limbus, and spiral ganglion neurons. NPR-A expression was found in gateways critical for K+ influx into a cellular network or efflux from a cell into the endolymph, a high K+ extracellular fluid unique to the cochlea. Furthermore, NPR-A was also found in type I neurons that are critical for neurotransmission, implicating a regulatory role for ANP directly in the sensory pathway.NPR-A was intermittently co-localized with NKCC1 in the marginal and interdental cells, which are both exit points for K+ from the recycling system into the endolymph. NKCC1 may be an effector in these cells responsible for K+ efflux into the endolymph, but is likely only one of several, as co-localization was sporadic. In other cells where NPR-A was expressed, NKCC1 was clearly not the effector activated in the ANP pathway as no co-localization was observed. These studies provide novel information about the location of NPR-A in the cochlea and its relationship to other proteins, indicating a regulatory role for natriuretic peptides in both neurotransmission and K+ recycling in the mouse inner ear. Globally, determining the location of NPR-A in the cochlea identifies cellular targets for future molecular study of ANP action and the mechanisms for its regulation of hearing thresholds.Item Microbiological and chemical aspects of corrosion of sheet steel in the Duluth-Superior Harbor(2010-12) Bostrom, Jonathan RobertSteel structures in the Duluth-Superior harbor show unusual patterns of corrosion characterized by raised blister-like nodules called tubercles and pitted steel. This corrosion phenomenon could possibly decrease the integrity and the lifespan of the structures. Microbiological and chemical factors that may be influencing corrosion processes were examined in this study from 2007-2009. A laboratory microcosm experiment was designed to examine several microbiology and water quality parameters. Terminal-restriction fragment length polymorphism (T-RFLP) analyses showed that bacterial communities on steel were different from one another in microcosm treatments with different types of water (e.g. autoclaved Duluth-Superior harbor water vs. unaltered Duluth-Superior harbor water and Lake Superior water vs. Duluth-Superior harbor water). Coupons with different bacterial communities also showed differences in sulfate-reducing bacterial abundance and iron-oxidizing bacterial abundance. Further, coupons with higher abundances of sulfate-reducing bacteria and iron-oxidizing bacteria had higher inverse polarization resistance values. Inverse polarization resistance is frequently used to approximate the instantaneous rate of corrosion. Mass lost and pit depth were measured on steel in the microcosm, and these two measurements showed a positive correlation. Microbiological and corrosion measurements were also performed on steel in the Duluth-Superior harbor, and these measurements were compared to steel in the microcosm experiment. These experiments showed correlations among water chemistry, bacterial community, and populations of specific bacteria that are associated with corrosion in other ecosystems.Item Nutrient regeneration by the zooplankton community in the deep chlorophyll layer of Lake Superior(2012-08) Oliver, Samantha KayItem Optimization of a hibernation-based small-volume resuscitation fluid(2014-09) Pérez de Lara Rodríguez, Cecilia EdnaBackground: Hemorrhagic shock is the number one cause of preventable deaths after trauma. Hibernation exemplifies a physiological state in which blood flow is reduced to a magnitude comparable to that of hemorrhagic shock. However, hibernators are naturally shielded from the insults that a similar reduction in blood flow would cause in a non-hibernating mammal. Our laboratory previously published a small volume resuscitation fluid based on hibernation physiology:BHB/M. It has three main components: 1) 4 M BHB, 2) 43 mM melatonin, and 3) 20% DMSO. Only the indicated concentration of each component of BHB/M has been previously tested. For that reason, worked towards the optimization of the composition and delivery of BHB/M in order to enhance survival in a rat model of hemorrhagic shock.Methods and Results: Previously, BHB/M was given as a 1 ml/kg bolus followed by a 100 µl/hr slow infusion. BHB/M was administered as either a single bolus or a bolus plus slow infusion in acutely operated rats. There were no statistical differences (p>0.05) in mean survival times when comparing the bolus only (mean survival 496.67 ± 314.59 min. n=6) to the bolus plus slow infusion (mean survival 149.20 ±142.71 min. n=5) protocol.Two separate dose-ranging studies were conducted for both BHB and Melatonin. In the BHB dose-ranging study, BHB was administered at either a 4 M,2 M, or 0.4 M concentration in conjunction with 4.3 mM melatonin and 10% DMSO. 10-day mean survival showed a dose-dependent trend where the higher the concentration of BHB infused the longer the rats survived (4 M BHB, 7.38 ± 1.75 days; 2 M BHB, 5.25 ± 2.22 days; 0.4 M BHB, 2.07 ± 2.05 days). In the melatonin dose-ranging study, melatonin was administered at either a 4.3 mM, 0.43 mM 0.0043 mM, 0.000043 mM, or 0 mM concentration in conjunction with 4 M BHB and 2% DMSO. An osmolarity control composed of 4 M NaCl and 0.000043 mM melatonin in 2 % DMSO was also included. Administering 4 M BHB without melatonin resulted in very low mean survival times (4.38 ± 1.42 days); the same was true when infusing 0.000043 mM melatonin with 4 M NaCl (4.58 ± 1.42). All treatments containing both 4 M BHB and melatonin, regardless of concentration, resulted in mean survival times of ~7.5 days.A large-volume experiment was conducted in order to compare isotonic BHB/M to the standard of care (LR). Rats subjected to 60% blood loss were infused with either LR, LR plus 4.3 mM melatonin, 140 mM BHB with 1.5x10-6 mM Mel, or 140 mM BHB with 4.3 mM Mel. LR and LR plus 4.3 mM melatonin had statistically higher (p<0.05) mean survival times (7.35 ± 1.59 days and 6.73 ± 1.57 days, respectively) than 140 mM BHB with 1.5x10-6 mM Mel (2.08 ± 1.18 days).Conclusions: BHB/M can be administered as a single 1 ml/kg bolus; following the bolus with a 100 µl/hr slow infusion is not necessary to obtain a maximum survival benefit. BHB must be administered at a 4 M concentration as there is a dose-dependent trend in which the lower the concentration of BHB administered the lower the percent survival to 10 days. Melatonin provides therapeutic effects at very low concentrations evident by the survival observed when administering a solution containing melatonin at a concentration a million-fold lower than previously published. Furthermore, melatonin is essential for survival since 4 M BHB without melatonin had a considerably reduced survival rate. A large volume dilute BHB/M is not a viable alternative to the standard of care.Item PIN6, an auxin efflux transporter, is essential for nectar secretion in Arabidopsis thaliana.(2011-06) Fekete, MeganNectar plays a vital role in plant reproductive success by attracting pollinators. Although much is known about the structural aspects of nectaries as well as the chemical composition of nectar from a host of species, there is little understanding on how a plant controls its nectar phenotype at a molecular level. Plant hormones, such as jasmonic acid, gibberellic acid, and auxin, are essential for proper development and their influence on nectar secretion was the focus of some early studies, but produced conflicting results. With our group’s identification of auxin-related genes preferentially expressed in Arabidopsis thaliana nectaries, it became clear that auxin might have an important role in regulating nectar secretion in the Brassicaceae. For example, multiple mutants for an irregular auxin efflux protein, PIN6, from Arabidopsis thaliana were identified. Distinct phenotypes and nectar outputs were identified with the various PIN6 mutants, including a mutant with a 30% increase in nectar sugar output (pin6-1) and a mutant with trace nectar sugar output (pin6-2). A positive correlation of nectar volume with PIN6 gene expression was found. Additionally, Arabidopsis thaliana, Brassica rapa, and various other flowers were cultured in solutions containing auxin and auxin transport inhibitors to determine auxin’s influence on nectar production in these species. PIN6 is essential for nectar secretion in A. thaliana and proper cellular auxin transport is needed to maintain typical nectar volumes, as well as for the expression of multiple key auxin genes. Manipulation of local auxin concentrations in the nectaries could potentially lead to the development of plants with traits that increase attractiveness to pollinators.Item Prevalence of the gene lsr2 among the genus Mycobacterium and an investigation into changes in biofilm formation when inactivating lsr2 regulated genes in Mycobacterium smegmatis(2014-10) Gatlin, Wayne CharlesMycobacterium smegmatis is a non-pathogenic model organism commonly used to study the human pathogen Mycobacterium tuberculosis. M. smegmatis has a rough colony morphology and is capable of forming biofilms, however, when the DNA-regulating protein Lsr2 is inactivated the bacteria forms a smooth colony and loses biofilm formation. This study investigates the phenotypic effect on colony morphology and biofilm formation when Lsr2-regulated genes are inactivated. A mutant strain of M. smegmatis with defective lsr2 (M. smegmatis Δlsr2) was used as a parent strain for the study and the gene for mycocerosic acid synthase (mas) was selected for inactivation. Genes downstream of mas from MSMEG_4727 to MSMEG_4733 and MSMEG_4741were also selected for inactivation. Genes were inactivated using homologous recombination via "suicide vector" plasmids lacking a Mycobacterial origin of replication and carrying kanamycin resistance and PCR fragments of the target genes. M. smegmatis Δlsr2 was transformed by electroporation and transformants were plated and screened for kanamycin resistance. The mutant strain lacking functional lsr2 and mas (M. smegmatis Δlsr2Δmas) regained the ability to form biofilms and exhibited colony morphology similar to wild-type M. smegmatis. Inactivation of genes MSMEG_4727 to MSMEG_4733 produced similar results. Inactivation of MSMEG_4741 caused no change in the Δlsr2 mutant phenotype. These results indicate that mas and genes downstream are involved with the biofilm formation and colony morphology change associated with the M. smegmatis Δlsr2 mutant strain.Item Role of hybrid cluster protein 4 in anaerobic metabolism in Chlamydomonas reinhardtii(2011-09) Olson, AdamThe unicellular green algae Chlamydomonas reinhardtii (C. reinhardtii) has long been studied for its unique fermentation pathways and is recently being considered as a candidate organism in biofuel production. Fermentation in C. reinhardtii is facilitated by a network of three predominant pathways producing four major by products: formate, ethanol, acetate and hydrogen. Recent microarray studies have identified many previously unknown genes highly up-regulated during anaerobiosis, and new tools for the targeted gene disruption make reverse genetics possible in C. reinhardtii for the first time. For example, hybrid cluster protein 4 (HCP4) is one of the most highly up-regulated genes during anaerobiosis in C. reinhardtii, displaying a nearly 1,600 fold increase upon anoxia. Hybrid cluster proteins have long been studied for their unique spectroscopic properties, yet their biological functions remain unclear. In this study HCP4 was knocked down using artificial microRNAs, followed by extensive phenotypic analyses. This study shows that knockdown of HCP4 affects the regulation of many key fermentative genes as well as metabolic flux and nitrogen uptake.