Matching Items (166)
Description
Biological soil crusts (BSCs) are critical components of arid and semiarid environments and provide the primary sources of bioavailable macronutrients and increase micronutrient availability to their surrounding ecosystems. BSCs are composed of a variety of microorganisms that perform a wide range of physiological processes requiring a multitude of bioessential micronutrients, such as iron, copper, and molybdenum. This work investigated the effects of BSC activity on soil solution concentrations of bioessential elements and examined the microbial production of organic chelators, called siderophores. I found that aluminum, vanadium, copper, zinc, and molybdenum were solubilized in the action of crusts, while nickel, zinc, arsenic, and zirconium were immobilized by crust activity. Potassium and manganese displayed behavior consistent with biological removal and mobilization, whereas phosphorus and iron solubility were dominated by abiotic processes. The addition of bioavailable nitrogen altered the effects of BSCs on soil element mobilization. In addition, I found that the biogeochemical activites of BSCs were limited by molybdenum, a fact that likely contributes to co-limitation by nitrogen. I confirmed the presence of siderophore producing microbes in BSCs. Siderophores are low-molecular weight organic compounds that are released by bacteria to increase element solubility and facilitate element uptake; siderophore production is likely the mechanism by which BSCs affect the patterns I observed in soil solution element concentrations. Siderophore producers were distributed across a range of bacterial groups and ecological niches within crusts, suggesting that siderophore production influences the availability of a variety of elements for use in many physiological processes. Four putative siderophore compounds were identified using electrospray ionization mass spectrometry; further attempts to characterize the compounds confirmed two true siderophores. Taken together, the results of my work provide information about micronutrient cycling within crusts that can be applied to BSC conservation and management. Fertilization with certain elements, particularly molybdenum, may prove to be a useful technique to promote BSC growth and development which would help prevent arid land degradation. Furthermore, understanding the effects of BSCs on soil element mobility could be used to develop useful biomarkers for the study of the existence and distribution of crust-like communities on ancient Earth, and perhaps other places, like Mars.
ContributorsNoonan, Kathryn Alexander (Author) / Hartnett, Hilairy (Thesis advisor) / Anbar, Ariel (Committee member) / Garcia-Pichel, Ferran (Committee member) / Shock, Everett (Committee member) / Sharp, Thomas (Committee member) / Arizona State University (Publisher)
Created2012
Description
Parental care provides many benefits to offspring. One widely realized benefit is enhanced regulation of offspring's thermal environment. The developmental thermal environment during development can be optimized behaviorally through nest site selection and brooding, and it can be further enhanced by physiological heat production. In fact, enhancement of the developmental thermal environment has been proposed as the initial driving force for the evolution of endothermy in bird and mammals. I used pythons (Squamata: Pythonidae) to expand existing knowledge of behavioral and physiological parental tactics used to regulate offspring thermal environment. I first demonstrated that brooding behavior in the Children's python (Antaresia childreni) is largely driven by internal mechanisms, similar to solitary birds, suggesting that the early evolution of the parent-offspring association was probably hormonally driven. Two species of python are known to be facultatively thermogenic (i.e., are endothermic during reproduction). I expand current knowledge of thermogenesis in Burmese pythons (Python molurus) by demonstrating that females use their own body temperature to modulate thermogenesis. Although pythons are commonly cited as thermogenic, the actual extent of thermogenesis within the family Pythonidae is unknown. Thus, I assessed the thermogenic capability of five previously unstudied species of python to aid in understanding phylogenetic, morphological, and distributional influences on thermogenesis in pythons. Results suggest that facultative thermogenesis is likely rare among pythons. To understand why it is rare, I used an artificial model to demonstrate that energetic costs to the female likely outweigh thermal benefits to the clutch in species that do not inhabit cooler latitudes or lack large energy reserves. In combination with other studies, these results show that facultative thermogenesis during brooding in pythons likely requires particular ecological and physiological factors for its evolution.
ContributorsBrashears, Jake (Author) / DeNardo, Dale (Thesis advisor) / Harrison, Jon (Committee member) / Deviche, Pierre (Committee member) / McGraw, Kevin (Committee member) / Smith, Andrew (Committee member) / Arizona State University (Publisher)
Created2012
Description
Self-maintenance behaviors, like preening in birds, can have important effects on fitness in many animals. Birds produce preen oil, which is a mixture of volatile and non-volatile compounds, that is spread through their feathers during grooming and influences feather integrity, waterproofing, and coloration. As urban areas grow and present conditions that may demand increased feather self-maintenance (e.g. due to soiling, pollution, elevated UV exposure due to natural habitat alterations), it is important to examine how preening and preen oil may be affected by this process. I assessed variation in preen oil composition in house finches (Haemorhous mexicanus) as a function of sex, urbanization, and plumage hue, a sexually selected indicator of male quality. Preen oil samples from birds captured at urban and rural sites were analyzed using gas chromatography-mass spectrometry. We detected 18 major peaks, which we tentatively identified as esters, and found that, although there were no sex or urban-rural differences in preen oil constituents, there was a significant interactive effect of sex and urbanization, with rural females and urban males having higher amounts of some components. This suggests that factors that vary with sex or urbanization, such as the timing of seasonal cycles, are affecting preen oil composition. There were no significant relationships between coloration and preen oil composition, suggesting that preen oil composition does not vary with male quality.
ContributorsBrooks, Ellen Elizabeth (Author) / McGraw, Kevin (Thesis director) / Liebig, Juergen (Committee member) / Weaver, Melinda (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
Depletion of fossil fuel resources has led to the investigation of alternate feedstocks for and methods of chemical synthesis, in particular the use of E. coli biocatalysts to produce fine commodity chemicals from renewable glucose sources. Production of phenol, 2-phenylethanol, and styrene was investigated, in particular the limitation in yield and accumulation that results from high product toxicity. This paper examines two methods of product toxicity mitigation: the use of efflux pumps and the separation of pathways which produce less toxic intermediates. A library of 43 efflux pumps from various organisms were screened for their potential to confer resistance to phenol, 2-phenylethanol, and styrene on an E. coli host. A pump sourced from P. putida was found to allow for increased host growth in the presence of styrene as compared to a cell with no efflux pump. The separation of styrene producing pathway was also investigated. Cells capable of performing the first and latter halves of the synthesis were allowed to grow separately and later combined in order to capitalize on the relatively lower toxicity of the intermediate, trans-cinnamate. The styrene production and yield from this separated set of cultures was compared to that resulting from the growth of cells containing the full set of styrene synthesis genes. Results from this experiment were inconclusive.
ContributorsLallmamode, Noor Atiya Jabeen (Author) / Nielsen, David (Thesis director) / Cadillo-Quiroz, Hinsby (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
Nitrous oxide (N2O) is a major contributor to the greenhouse effect and to stratospheric ozone depletion. In soils, nitrogen reduction is performed by biotic and abiotic processes, including microbial denitrification and chemical denitrification. Chemical denitrification, or chemodenitrification, is the abiotic step-wise reduction of nitrate (NO3-), nitrite (NO2-), or nitric oxide (NO) to N2O in anoxic environments, with high turnover rates particularly in acidic soils. Chemodenitrification was identified in various environments, but the mechanism is still not understood. In this study, the factors influencing abiotic reduction of NO2- to N2O in acidic tropical peat soil are examined. These factors include pH, organic matter content, and dissolved ferrous iron. Anoxic peat soil from sites located in the Peruvian Amazon was used for incubations. The results show that peat soil (pH ~4.5) appears to reduce NO2- more quickly in the presence of lower pH and higher Fe(II) concentrations. NO2- is completely reduced in excess Fe(II), and Fe(II) is completely oxidized in excess NO2-, providing evidence for the proposed mechanism of chemodenitrification. In addition, first order reaction rate constants kFe(II) and kNO2- were calculated using concentration measurements over 4 hours, to test for the hypothesized reaction rate relationships kFe(II): kFe(II) kFe(II)~NO2- > kFe(II)>NO2- and kNO2-: kFe(II)NO2-. The NO2- k values followed the anticipated pattern, although the Fe(II) k value data was inconclusive. Organic material may also play a role in NO2- reduction through chemodenitrification, and future experimentation will test this possibility. How and to what extent the pH and the concentrations of organic matter and Fe(II) affect the kinetic rate of chemodenitrification will lend insight into the N2O production potential of natural tropical peatlands.
ContributorsTylor, Kaitlyn Marie (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / Day, Thomas (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This thesis explores and analyzes the emergence of for-profit stem cell clinics in the United States, specifically in the Phoenix metropolitan area. Stem cell therapy is an emerging field that has great potential in preventing or treating a number of diseases. Certain companies are currently researching the application of stem cells as therapeutics. At present the FDA has only approved one stem cell-based product; however, there are a number of companies currently offering stem cell therapies. In the past five years, most news articles discussing these companies offering stem cell treatments talk of clinics in other countries. Recently, there seems to be a number of stem cell clinics appearing in the United States. Using a web search engine, fourteen stem cell clinics were identified and analyzed in the Phoenix metropolitan area. Each clinic was analyzed by their four key characteristics: business operations, stem cell types, stem cell isolation methods, and their position with the FDA. Based off my analysis, most of the identified clinics are located in Scottsdale or Phoenix. Some of these clinics even share the same location as another medical practice. Each of the fourteen clinics treat more than one type of health condition. The stem clinics make use of four stem cell types and three different isolation methods to obtain the stem cells. The doctors running these clinics almost always treat health conditions outside of their expertise. Some of these clinics even claim they are not subject to FDA regulation.
ContributorsAmrelia, Divya Vikas (Author) / Brafman, David (Thesis director) / Frow, Emma (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Methane (CH4) is very important in the environment as it is a greenhouse gas and important for the degradation of organic matter. During the last 200 years the atmospheric concentration of CH4 has tripled. Methanogens are methane-producing microbes from the Archaea domain that complete the final step in breaking down organic matter to generate methane through a process called methanogenesis. They contribute to about 74% of the CH4 present on the Earth's atmosphere, producing 1 billion tons of methane annually. The purpose of this work is to generate a preliminary metabolic reconstruction model of two methanogens: Methanoregula boonei 6A8 and Methanosphaerula palustris E1-9c. M. boonei and M. palustris are part of the Methanomicrobiales order and perform hydrogenotrophic methanogenesis, which means that they reduce CO2 to CH4 by using H2 as their major electron donor. Metabolic models are frameworks for understanding a cell as a system and they provide the means to assess the changes in gene regulation in response in various environmental and physiological constraints. The Pathway-Tools software v16 was used to generate these draft models. The models were manually curated using literature searches, the KEGG database and homology methods with the Methanosarcina acetivorans strain, the closest methanogen strain with a nearly complete metabolic reconstruction. These preliminary models attempt to complete the pathways required for amino acid biosynthesis, methanogenesis, and major cofactors related to methanogenesis. The M. boonei reconstruction currently includes 99 pathways and has 82% of its reactions completed, while the M. palustris reconstruction includes 102 pathways and has 89% of its reactions completed.
ContributorsMahendra, Divya (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / Wang, Xuan (Committee member) / Stout, Valerie (Committee member) / Barrett, The Honors College (Contributor) / Computing and Informatics Program (Contributor) / School of Life Sciences (Contributor) / Biomedical Informatics Program (Contributor)
Created2014-05
Description
Testosterone (T) is a steroid hormone that affects behavior and reproductive traits (e.g. spermatogenesis and ornamentation) in vertebrates. In addition to long-term influences, T can rapidly increase in males following aggressive male-male encounters. Less is known how females directly influence male T and behavior, though research with humans suggests that sexually attractive females elicit a greater increase in male T and reproductive behavior than unattractive females. In birds, the influence of female attractiveness on male T and behavior is currently untested. We hypothesized that T and courtship behavior in male zebra finches would correlate with female attractiveness. We used red leg bands to make females "attractive" and green bands to make them "unattractive" (unbanded females were controls) as previous research suggests that zebra finches prefer red colors over green in mating contexts. We collected blood from males before and after "speed-dating" trials to measure changes in plasma T and analyzed male courtship behaviors from trial video recordings. The likelihood of plasma T increasing after a trial was significantly greater in males who were with red-banded females compared to control females, suggesting males may find them more attractive than green or control females. Additionally, independent of band color, males who exhibited greater T differences initiated courtship sooner and spent more time closest to females. However, courtship initiation and time spent near females were not correlated with band color. Overall, our results suggest that female attractiveness can influence male reproductive physiology, but the presence of a female may trigger male courtship behavior.
ContributorsBero-Buell, Brianna Danielle (Author) / McGraw, Kevin (Thesis director) / Deviche, Pierre (Committee member) / Ligon, Russell (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2014-05
Description
Historically, the study of cognition has focused on species-specific learning, memory, problem-solving and decision-making capabilities, and emphasis was placed on the few high-performing individuals who successfully completed cognitive tasks. Studies often deemed the success of a small fraction of individuals as suggestive of the cognitive capacity of the entire species. Recently though, interest in individual variation in cognitive ability within species has increased. This interest has emerged concomitantly with studies of variation in animal personalities (i.e. behavioral syndromes). Cognitive ability may be closely tied to personality because the mechanisms by which an individual perceives and uses environmental input (cognition) should influence how that individual consistently responds to various ecological demands (personality). However, empirical support for links between animal cognition and behavioral syndromes is currently lacking. I examined individual variation in cognition and personality in male veiled chameleons, Chamaeleo calyptratus. I considered three axes of personality (aggression, activity, and exploratory behavior) and cognition in a foraging context using visual cues − specifically, the ability to associate a color with a food reward. I found that aggression was positively correlated with the proportion of correct choices and number of consecutive correct choices. Also, one measure of exploration (the number of vines touched in a novel environment) was correlated negatively with the proportion of correct choices and positively with the number of consecutive incorrect decisions. My investigation suggests that more aggressive, less exploratory chameleons were more successful learners, and that there exists a shared pathway between these personality traits and cognitive ability.
ContributorsBruemmer, Sarah Adele (Author) / McGraw, Kevin (Thesis director) / Rutowski, Ronald (Committee member) / Ligon, Russell (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution and Social Change (Contributor) / School of Life Sciences (Contributor)
Created2013-05
Description
Urbanization exposes wildlife to many unfamiliar environmental conditions, including the presence of novel structures and food sources. Adapting to or thriving within such anthropogenic modifications may involve cognitive skills, whereby animals come to solve novel problems while navigating, foraging, etc. The increased presence of humans in urban areas is an additional environmental challenge that may potentially impact cognitive performance in wildlife. To date, there has been little experimental investigation into how human disturbance affects problem solving in animals from urban and rural areas. Urban animals may show superior cognitive performance in the face of human disturbance, due to familiarity with benign human presence, or rural animals may show greater cognitive performance in response to the heightened stress of unfamiliar human presence. Here, I studied the relationship between human disturbance, urbanization, and the ability to solve a novel foraging problem in wild-caught juvenile house finches (Haemorhous mexicanus). This songbird is a successful urban dweller and native to the deserts of the southwestern United States. In captivity, finches captured from both urban and rural populations were presented with a novel foraging task (sliding a lid covering their typical food dish) and then exposed to regular periods of high or low human disturbance over several weeks before they were again presented with the task. I found that rural birds exposed to frequent human disturbance showed reduced task performance compared to human-disturbed urban finches. This result is consistent with the hypothesis that acclimation to human presence protects urban birds from reduced cognition, unlike rural birds. Some behaviors related to solving the problem (e.g. pecking at and eying the dish) also differed between urban and rural finches, possibly indicating that urban birds were less neophobic and more exploratory than rural ones. However, these results were unclear. Overall, these findings suggest that urbanization and acclimation to human presence can strongly predict avian response to novelty and cognitive challenges.
ContributorsCook, Meghan Olivia (Author) / McGraw, Kevin (Thesis director) / Bimonte-Nelson, Heather (Committee member) / Weaver, Melinda (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2015-05