Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 93-109). Available also in a digital version from Dissertation Abstracts.

L'objectiu d'aquest estudi és el d'investigar sobre l'ús de matèria orgànica per part dels fongs i bacteris que colonitzen diferents substrats bentònics en rius Mediterranis i analitzar l'efecte dels factors ambientals i antròpics sobre l'estabilitat estructural i funcional de les comunitats del biofilm. La metodologia emprada en aquest estudi consisteix en: i) anàlisi de la biomassa bacteriana i fúngica, ii) anàlisi de la composició de les comunitats bentòniques (identificació d'hifomicets aquàtics i anàlisi del 16S rDNA bacterià), i iii) anàlisi de l'activitat enzimàtica extracel·lular relacionada amb el reciclatge de matèria orgànica en rius. / This study aimed to investigate on the use of organic matter by fungi and bacteria inhabiting different benthic substrata and to analyze the effect of environmental and anthropogenic perturbations on the structural and functional stability of biofilms. The following methodologies has been used in this study: i) analysis of fungal and bacterial biomass, ii) analysis of benthic community composition (identification of hyphomycete taxa, analysis of the bacterial 16S rDNA), and iii) analysis of extracellular enzyme activities involved in organic matter recycling in rivers.

A utilização de inóculos líquidos na produção de Shiitake (Lentinula edodes (Berk.) Pegler) é uma tecnologia promissora para a industrialização do cultivo em sistema axênico, uma vez que permite a inoculação do micélio de forma rápida e bem distribuída, reduzindo riscos de contaminação e o período de incubação dos substratos. Neste trabalho, o cultivo submerso para a produção de micélio de Shiitake foi avaliado em um biorreator airlift de circulação externa, idealizado e projetado no grupo, utilizando o meio de cultura Mushroom Complete Medium adicionado de micronutrientes, nas condições de operação: taxas de aeração: 0.16, 0.20, e 0.24 vvm e tamanhos de inóculo (i.s.): 1.0 g.L-1 e 2.0 g.L-1. Na melhor condição de operação (0.16 vvm e 1.0 g.L-1 i.s.), um modelo matemático foi desenvolvido usando o software EMSO para descrever a cinética da cultura em ajuste aos dados experimentais. Foram atingidos 15,47 g.L-1 de biomassa total, após 10 dias de cultivo, 0,516 d-1 de taxa máxima de crescimento específico, fatores de rendimento Yx/s 1,06 g.g-1, YP/X 0,485 (g.L-1).g-1, YP/S 0,140 (g.L-1).g-1 e produtividade PX 0,061 (g.L-1).h-1. A predição do modelo demonstrou ser um parâmetro confiável para estudos de aumento de escala já que descreveu bons resultados preditivos para biomassa em relação aos produtos do metabolismo (CO2 e síntese de H+ pela acidificação do meio) e ao consumo de nutrientes (O2 e glicose). A seleção e a avaliação de linhagens no cultivo também são fatores a serem considerados para obtenção de boas produtividades e, deste modo, o desempenho produtivo de cinco linhagens de Shiitake foi avaliado em cultivo axênico, utilizando um planejamento composto central (CCD) para avaliar as variáveis independentes: tempo de incubação I(t), e percentual de farelo de trigo em relação a serragem Eucalypitus saligna (representada pela relação carbono/nitrogênio (RC/N)), tendo a eficiência biológica (BE) e o peso unitário dos cogumelos como resultados de destino . Os substratos utilizados tiveram sua composição físico-química determinada e as taxas de suplementação do substrato foram otimizadas, não só para o rendimento em cultivo, mas também para o crescimento vegetativo do micélio. Os melhores resultados de BE em todas as linhagens foram obtidos em cultivos com RC/N 57,62/1, com indução dos primórdios em 130 dias de I(t). Os cogumelos colhidos nesta condição de produção tiveram sua composição centesimal determinada. Atividades enzimáticas amilolíticas e celulolíticas, β-glicosidase e proteases específicas foram realizadas em ensaios de colonização do substrato. Três linhagens foram selecionadas para o isolamento de esporos e hibridização intraespecífica. As linhagens híbridas foram comparadas com as parentais em termos de rendimento e síntese das enzimas extracelulares. Os resultados deste trabalho demonstraram que a linhagem cultivada tem um efeito considerável sobre o rendimento, sobre o peso unitário e sobre a síntese de enzimas extracelulares produzidas pelo fungo, tanto pelas linhagens híbridas, como pelas parentais. / The use of liquid inoculant production of Shiitake (Lentinula edodes (Berk.) Pegler) is a promising technology for the industrialization farming of this fungus in axenic system because it allows the mycelium inoculation in a quick and well distributed way, thus reducing the risks of contamination and the incubation time of cultures. In this work, the submerged cultivation for the production of Shiitake mycelium was evaluated in an airlift bioreactor of external circulation, conceived and designed in the group, using the culture medium Mushroom Complete Medium added of micronutrients, under the operating conditions: rates of aeration: 0.16, 0.20, and 0.24 vvm and inoculum sizes (i.s.): 1.0 g. L-1 and 2.0 g. L-1. Under the best operating condition (0.16 vvm and 1.0 g L-1 i.s.), a mathematical model was developed using the EMSO software to describe the kinetics of culture fittnes to experimental data. It was possible to obtain 15.47 g L-1 of total biomass, after 10 days of cultivation, a maximum specific growth rate of 0.516 d-1, yields of Yx/s 1,06 g.g-1, YP/X 0,485 (g.L-1).g-1, YP/S 0,140 (g.L-1).g-1 and PX (productivity) 0.061 (g.L-1).h-1. The prediction of the model has proven to be a reliable parameter for studies for scaling up because it was predictive for biomass considering the products of metabolism (CO2 and H+ synthesis by acidification of the medium) and nutrient consumption (O2 and glucose). The selection and evaluation of strains in cultivation are also factors to be considered to obtain good productivity and, therefore, the productive performance of five strains of Shiitake cultivated under axenic system, was carried out using a central composition design (CCD) to evaluate the independent variables: incubation time I(t), and percentage of wheat bran in relation to sawdust of Eucalypitus saligna (represented by the carbon/nitrogen ratio (RC/N)), and having the biological efficiency (BE) and the unit weight of the mushrooms as target results. The best results for BE for all the strains were obtained in cultures with RC/N 57.62/1, with primordia induced at 130 days of I(t). The substrates used had their physico-chemical composition determined and the rates of substrate supplementation have been optimized, not only for the cultivation yields, but also for vegetative growth of the mycelium. The mushrooms harvested in this condition of production had their centesimal composition determined. Amilolytic, cellulolytic, β-glucosidase and specific proteases activities were performed in tests of colonization of the substrate. Three strains were selected for the isolation of spores and intraspecific hybridization was carried out. Hybrid strains were compared with the parental strains in terms of yields and synthesis of extracellular enzymes. The results of this study showed that strain has a considerable effect on both the yield and the unit weight of mushrooms.

Doctor of Philosophy / Department of Agronomy / Charles W. Rice / Gretchen F. Sassenrath / Soil microorganisms are a critical component of ecosystem services provided by soil. Soil management drives soil physical, chemical, and biological properties. Pedogenesis and management interact to change microbial structure and function in the soil profile. Soil microbial properties may vary temporally with crop development and crop species. The objective of this study was to explore the pedogenetic and anthropogenic controls on key soil microbial properties by (i) assessing the profile of a claypan soil under conventional tillage (CT), no-till (NT), and hay meadow (HM); (ii) assessing seasonal changes of soil microbial properties in a corn/winter wheat/soybean rotation under CT and NT; and (iii) assessing vertical changes of soil microbial properties in response to long-term (28 yrs) tillage and mineral and organic fertilization. Selected microbial properties included extracellular enzyme activity, microbial structure as measured by phospholipid fatty acid (PLFA), as well as soil chemical properties. Soil C, enzyme activities, and microbial biomass were greatest in HM soils, followed by NT and then CT in the claypan soil. Wheat in the rotation increased hydrolase activity and bacterial biomass more than corn, while microbial activities were stable during soybean growth. Increased enzyme activities in the claypan layer resulted from the combination of clay-enzyme interaction and impacts from management practices. In a Mollisol soil, an increase in C-acquiring enzyme activity and microbial PLFAs in a buried A horizon was a result of root growth under no-till practice and mineral fertilization. Surprisingly, long-term mineral fertilizer applications had little effect on enzyme activities and microbial biomass. Long-term organic fertilization increased soil C, enzyme activities, and PLFAs but decreased arbuscular mycorrhizal fungi (AMF) throughout the soil profile to a depth of 90 cm. Microbial properties are controlled by crop and soil management at the soil surface and by the interaction of management and pedogenetic properties deeper in the soil profile. Incorporating grasses in the crop rotation may allow nutrients to be extracted from deeper within the soil profile, enhancing the utilization of the entire soil profile and providing additional nutrient resources to cash crops. Incorporating wheat in the crop rotation supports greater microbial activity and biomass after corn harvest, especially in no-till management. Additional research is required to delineate further causative factors impacting enzyme activity in the claypan layer, a finer resolution in soil microbial community at the species level to explore the linkage between ecological function and microbiome structure, and a network analysis for the soil-plant-microbe interactions.

A utilização de inóculos líquidos na produção de Shiitake (Lentinula edodes (Berk.) Pegler) é uma tecnologia promissora para a industrialização do cultivo em sistema axênico, uma vez que permite a inoculação do micélio de forma rápida e bem distribuída, reduzindo riscos de contaminação e o período de incubação dos substratos. Neste trabalho, o cultivo submerso para a produção de micélio de Shiitake foi avaliado em um biorreator airlift de circulação externa, idealizado e projetado no grupo, utilizando o meio de cultura Mushroom Complete Medium adicionado de micronutrientes, nas condições de operação: taxas de aeração: 0.16, 0.20, e 0.24 vvm e tamanhos de inóculo (i.s.): 1.0 g.L-1 e 2.0 g.L-1. Na melhor condição de operação (0.16 vvm e 1.0 g.L-1 i.s.), um modelo matemático foi desenvolvido usando o software EMSO para descrever a cinética da cultura em ajuste aos dados experimentais. Foram atingidos 15,47 g.L-1 de biomassa total, após 10 dias de cultivo, 0,516 d-1 de taxa máxima de crescimento específico, fatores de rendimento Yx/s 1,06 g.g-1, YP/X 0,485 (g.L-1).g-1, YP/S 0,140 (g.L-1).g-1 e produtividade PX 0,061 (g.L-1).h-1. A predição do modelo demonstrou ser um parâmetro confiável para estudos de aumento de escala já que descreveu bons resultados preditivos para biomassa em relação aos produtos do metabolismo (CO2 e síntese de H+ pela acidificação do meio) e ao consumo de nutrientes (O2 e glicose). A seleção e a avaliação de linhagens no cultivo também são fatores a serem considerados para obtenção de boas produtividades e, deste modo, o desempenho produtivo de cinco linhagens de Shiitake foi avaliado em cultivo axênico, utilizando um planejamento composto central (CCD) para avaliar as variáveis independentes: tempo de incubação I(t), e percentual de farelo de trigo em relação a serragem Eucalypitus saligna (representada pela relação carbono/nitrogênio (RC/N)), tendo a eficiência biológica (BE) e o peso unitário dos cogumelos como resultados de destino . Os substratos utilizados tiveram sua composição físico-química determinada e as taxas de suplementação do substrato foram otimizadas, não só para o rendimento em cultivo, mas também para o crescimento vegetativo do micélio. Os melhores resultados de BE em todas as linhagens foram obtidos em cultivos com RC/N 57,62/1, com indução dos primórdios em 130 dias de I(t). Os cogumelos colhidos nesta condição de produção tiveram sua composição centesimal determinada. Atividades enzimáticas amilolíticas e celulolíticas, β-glicosidase e proteases específicas foram realizadas em ensaios de colonização do substrato. Três linhagens foram selecionadas para o isolamento de esporos e hibridização intraespecífica. As linhagens híbridas foram comparadas com as parentais em termos de rendimento e síntese das enzimas extracelulares. Os resultados deste trabalho demonstraram que a linhagem cultivada tem um efeito considerável sobre o rendimento, sobre o peso unitário e sobre a síntese de enzimas extracelulares produzidas pelo fungo, tanto pelas linhagens híbridas, como pelas parentais. / The use of liquid inoculant production of Shiitake (Lentinula edodes (Berk.) Pegler) is a promising technology for the industrialization farming of this fungus in axenic system because it allows the mycelium inoculation in a quick and well distributed way, thus reducing the risks of contamination and the incubation time of cultures. In this work, the submerged cultivation for the production of Shiitake mycelium was evaluated in an airlift bioreactor of external circulation, conceived and designed in the group, using the culture medium Mushroom Complete Medium added of micronutrients, under the operating conditions: rates of aeration: 0.16, 0.20, and 0.24 vvm and inoculum sizes (i.s.): 1.0 g. L-1 and 2.0 g. L-1. Under the best operating condition (0.16 vvm and 1.0 g L-1 i.s.), a mathematical model was developed using the EMSO software to describe the kinetics of culture fittnes to experimental data. It was possible to obtain 15.47 g L-1 of total biomass, after 10 days of cultivation, a maximum specific growth rate of 0.516 d-1, yields of Yx/s 1,06 g.g-1, YP/X 0,485 (g.L-1).g-1, YP/S 0,140 (g.L-1).g-1 and PX (productivity) 0.061 (g.L-1).h-1. The prediction of the model has proven to be a reliable parameter for studies for scaling up because it was predictive for biomass considering the products of metabolism (CO2 and H+ synthesis by acidification of the medium) and nutrient consumption (O2 and glucose). The selection and evaluation of strains in cultivation are also factors to be considered to obtain good productivity and, therefore, the productive performance of five strains of Shiitake cultivated under axenic system, was carried out using a central composition design (CCD) to evaluate the independent variables: incubation time I(t), and percentage of wheat bran in relation to sawdust of Eucalypitus saligna (represented by the carbon/nitrogen ratio (RC/N)), and having the biological efficiency (BE) and the unit weight of the mushrooms as target results. The best results for BE for all the strains were obtained in cultures with RC/N 57.62/1, with primordia induced at 130 days of I(t). The substrates used had their physico-chemical composition determined and the rates of substrate supplementation have been optimized, not only for the cultivation yields, but also for vegetative growth of the mycelium. The mushrooms harvested in this condition of production had their centesimal composition determined. Amilolytic, cellulolytic, β-glucosidase and specific proteases activities were performed in tests of colonization of the substrate. Three strains were selected for the isolation of spores and intraspecific hybridization was carried out. Hybrid strains were compared with the parental strains in terms of yields and synthesis of extracellular enzymes. The results of this study showed that strain has a considerable effect on both the yield and the unit weight of mushrooms.

A utilização de inóculos líquidos na produção de Shiitake (Lentinula edodes (Berk.) Pegler) é uma tecnologia promissora para a industrialização do cultivo em sistema axênico, uma vez que permite a inoculação do micélio de forma rápida e bem distribuída, reduzindo riscos de contaminação e o período de incubação dos substratos. Neste trabalho, o cultivo submerso para a produção de micélio de Shiitake foi avaliado em um biorreator airlift de circulação externa, idealizado e projetado no grupo, utilizando o meio de cultura Mushroom Complete Medium adicionado de micronutrientes, nas condições de operação: taxas de aeração: 0.16, 0.20, e 0.24 vvm e tamanhos de inóculo (i.s.): 1.0 g.L-1 e 2.0 g.L-1. Na melhor condição de operação (0.16 vvm e 1.0 g.L-1 i.s.), um modelo matemático foi desenvolvido usando o software EMSO para descrever a cinética da cultura em ajuste aos dados experimentais. Foram atingidos 15,47 g.L-1 de biomassa total, após 10 dias de cultivo, 0,516 d-1 de taxa máxima de crescimento específico, fatores de rendimento Yx/s 1,06 g.g-1, YP/X 0,485 (g.L-1).g-1, YP/S 0,140 (g.L-1).g-1 e produtividade PX 0,061 (g.L-1).h-1. A predição do modelo demonstrou ser um parâmetro confiável para estudos de aumento de escala já que descreveu bons resultados preditivos para biomassa em relação aos produtos do metabolismo (CO2 e síntese de H+ pela acidificação do meio) e ao consumo de nutrientes (O2 e glicose). A seleção e a avaliação de linhagens no cultivo também são fatores a serem considerados para obtenção de boas produtividades e, deste modo, o desempenho produtivo de cinco linhagens de Shiitake foi avaliado em cultivo axênico, utilizando um planejamento composto central (CCD) para avaliar as variáveis independentes: tempo de incubação I(t), e percentual de farelo de trigo em relação a serragem Eucalypitus saligna (representada pela relação carbono/nitrogênio (RC/N)), tendo a eficiência biológica (BE) e o peso unitário dos cogumelos como resultados de destino . Os substratos utilizados tiveram sua composição físico-química determinada e as taxas de suplementação do substrato foram otimizadas, não só para o rendimento em cultivo, mas também para o crescimento vegetativo do micélio. Os melhores resultados de BE em todas as linhagens foram obtidos em cultivos com RC/N 57,62/1, com indução dos primórdios em 130 dias de I(t). Os cogumelos colhidos nesta condição de produção tiveram sua composição centesimal determinada. Atividades enzimáticas amilolíticas e celulolíticas, β-glicosidase e proteases específicas foram realizadas em ensaios de colonização do substrato. Três linhagens foram selecionadas para o isolamento de esporos e hibridização intraespecífica. As linhagens híbridas foram comparadas com as parentais em termos de rendimento e síntese das enzimas extracelulares. Os resultados deste trabalho demonstraram que a linhagem cultivada tem um efeito considerável sobre o rendimento, sobre o peso unitário e sobre a síntese de enzimas extracelulares produzidas pelo fungo, tanto pelas linhagens híbridas, como pelas parentais. / The use of liquid inoculant production of Shiitake (Lentinula edodes (Berk.) Pegler) is a promising technology for the industrialization farming of this fungus in axenic system because it allows the mycelium inoculation in a quick and well distributed way, thus reducing the risks of contamination and the incubation time of cultures. In this work, the submerged cultivation for the production of Shiitake mycelium was evaluated in an airlift bioreactor of external circulation, conceived and designed in the group, using the culture medium Mushroom Complete Medium added of micronutrients, under the operating conditions: rates of aeration: 0.16, 0.20, and 0.24 vvm and inoculum sizes (i.s.): 1.0 g. L-1 and 2.0 g. L-1. Under the best operating condition (0.16 vvm and 1.0 g L-1 i.s.), a mathematical model was developed using the EMSO software to describe the kinetics of culture fittnes to experimental data. It was possible to obtain 15.47 g L-1 of total biomass, after 10 days of cultivation, a maximum specific growth rate of 0.516 d-1, yields of Yx/s 1,06 g.g-1, YP/X 0,485 (g.L-1).g-1, YP/S 0,140 (g.L-1).g-1 and PX (productivity) 0.061 (g.L-1).h-1. The prediction of the model has proven to be a reliable parameter for studies for scaling up because it was predictive for biomass considering the products of metabolism (CO2 and H+ synthesis by acidification of the medium) and nutrient consumption (O2 and glucose). The selection and evaluation of strains in cultivation are also factors to be considered to obtain good productivity and, therefore, the productive performance of five strains of Shiitake cultivated under axenic system, was carried out using a central composition design (CCD) to evaluate the independent variables: incubation time I(t), and percentage of wheat bran in relation to sawdust of Eucalypitus saligna (represented by the carbon/nitrogen ratio (RC/N)), and having the biological efficiency (BE) and the unit weight of the mushrooms as target results. The best results for BE for all the strains were obtained in cultures with RC/N 57.62/1, with primordia induced at 130 days of I(t). The substrates used had their physico-chemical composition determined and the rates of substrate supplementation have been optimized, not only for the cultivation yields, but also for vegetative growth of the mycelium. The mushrooms harvested in this condition of production had their centesimal composition determined. Amilolytic, cellulolytic, β-glucosidase and specific proteases activities were performed in tests of colonization of the substrate. Three strains were selected for the isolation of spores and intraspecific hybridization was carried out. Hybrid strains were compared with the parental strains in terms of yields and synthesis of extracellular enzymes. The results of this study showed that strain has a considerable effect on both the yield and the unit weight of mushrooms.

Yeasts form significant and important part of pedosphere microbiota. They keep nature balance, participate in cycles of elements and nutrients, are antagonists of various pathogens and as important decomposers, they produce the whole spectrum of different extracellular enzymes. The aim of this study was to determine the ability of yeasts, isolated from the soil adjacent to the fruit trees in Southwest Slovakia as well as from the contaminated soil (Pernek area, Slovakia), to produce extracellular enzymes. In total, 68 strains belonging to 45 different species were tested for the production of starch-like polysaccharide and for extracellular enzyme activities: polygalacturonases, lipases, proteases, cellulases, chitinases, -glucosidases and -amylases. This work was also focused on optimization of method for the yeast chitinase assay. Four methods were proved; two of them utilized liquid medium with chitin (colloidal and insoluble) as the sole carbon source and two others used solid plate methods with agar medium containing chitin. Based on results, cultivation in colloidal liquid chitin medium, terminated by the chitinase assay according to Ehrlich, was evaluated as the best method for detection of predominant exochitinase activity of yeasts. More than 75 % of tested yeasts exhibited some extracellular activity. Generally, the yeasts isolated from the soil under the fruit trees showed broader spectrum of enzyme activities than those originated from contaminated soils. Lipases, proteases and -glucosidases were found to be the most common activities. Only small proportion of yeasts was able to produce chitinases and/or cellulases. Aureobasidium pullulans, CCY 27-1-134, from the soil adjacent to the apple tree, showed the widest range of activities from all tested strains and it possessed all examined activities. On the other side, it did not produce starch-like polysaccharide. Tausonia (Trichosporon) pullulans and Cystofilobasidium macerans were the second most active producers of extracellular enzymes with variations in production of cellulases and -amylases. Representatives of the former polyphyletic genus Cryptococcus exhibited lipases, -glucosidases, -amylases and they were producers of the starch, but the interspecies differences were also noted. All strains of the genus Galactomyces were positive for polygalacturonases and the genera Candida and Cyberlindnera were positive for -glucosidases. All strains of Galactomyces candidum were tested for the production of polygalacturonases during 168 hours long cultivation on pectin media. Strain CCY 16-3-4 showed very stable growth on this medium and simultaneously exhibited significant amount of extracellular polygalactouronases. It has a potential to be very suitable producer of these enzymes but particular characterization of properties is necessary for its future use. Results of the screening showed that the production of extracellular enzymes is mostly strain-dependent and not species-dependent.

Membrane-based filtration technologies have seen rapid inclusion in a variety of industrial processes, especially production of drinking water by desalination. Biological fouling of membranes is a challenge that leads to increased costs from efficiency reductions, membrane damage, and ultimately, membrane replacement over time. Such costs can be mitigated by monitoring and optimizing cleaning processes for better prognosis. A fluorescence-based sensor for early biofouling detection capable of measuring extracellular enzyme activity was developed. The selected fluorogen and fluorogen-substrate were characterized and down selected by in vitro screening for compatibility in seawater and profiled over relevant Red Sea desalination parameters (pH and temperature). ATP measurements are currently regarded as start-of-the-art when assessing biomass accumulation in membrane-based filtration systems Therefore, the fluorescence sensor response was measured for a range of bacterial concentrations and validated using an ATP assay. We demonstrate the efficacy of the proposed approach for the quantitative assessment of bacteria activity in seawater rapidly and sensitively. Following in vitro testing, the method was employed in a lab-scale seawater reverse osmosis (SWRO) system for suitability in monitoring biofouling formation. The sensor successfully measured bacterial biomass accumulation rapidly and non-invasively using exogenously applied fluorogen-substrates. The sensor response was corroborated with real-time in situ non-destructive imaging of the membrane surface. This approach demonstrates the practicality of prototyping an early-detection biofouling sensor in membrane based processes using extracellular enzyme activity as a measure of bacterial abundance.

No description available.

Recent work in microbial ecology has focused on elucidating controls over biogeographic patterns and connecting microbial community composition to ecosystem function. My objective was to investigate the relative influences of landscape legacies and contemporary environmental factors on the distribution of soil microbial communities and their contribution to ecosystem processes across a glacial till sequence in Taylor Valley, Antarctica. Within each till unit, I sampled from dry areas and areas with visible evidence of recent surface water movement generated by seasonal melting of ephemeral snow packs and hillslope ground ice. Using T-RFLP 16S rRNA gene profiles of microbial communities, I analyzed the contribution of till and environmental factors to community similarity, and assessed the functional potential of the microbial community using extracellular enzyme activity assays. Microbial communities were influenced by geochemical differences among both tills and local environments, but especially organized by variables associated with water availability as the first axis of an NMDS ordination was strongly related to shifts in soil moisture content. CCA revealed that tills explained only 3.4% of the variability in community similarity among sites, while geochemical variables explained 18.5%. Extracellular enzyme activity was correlated with relevant geochemical variables reflecting the influence of nutrient limitation on microbial activity. In addition, enzyme activity was related to changes in community similarity, particularly in wet environments with a partial Mantel correlation of 0.32. These results demonstrate how landscape history and environmental conditions can shape the functional potential of a microbial community mediated through shifts in microbial community composition. / Master of Science