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Browsing by Subject "pathogens"

Now showing 1 - 5 of 5
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    Aquatic Plants from Minnesota Part 3 - Antimicrobial Effects
    (Water Resources Research Center, University of Minnesota, 1972-02) Abul-Hajj, Yusuf J.; Staba, E. John; Su, K. Lee
    In this study the antimicrobial activity of the following 22 Minnesotan aquatic plants was investigated: Anacharis Canadensis, Calla Polustris, Carex lacstris, Ceratophyllum demersum, Chara vulgaris, Elecharis smallii, Lemna minor, Myriophyllum exalbescens, Nuphar variegatum, Nymphaea turberosa, Potamogeton amplifolius, P. natans, P. pectinatus, P. richardsonu, P. zosteriformis, Sagittaria cuneata, S. latifolia, Sparganium eurycarpum, S. fluctuans, Typha angustifolia, Vallisneria amiercana, and Zizania aquetica, Furthermore, the chemical constituents responsible for the significant antimicrobial effect were isolated and identified. The skellysolve F. chloroform, 80% ethanol and fresh water extracts of plant species were treated for antimicrobial activity employing the qualitative filter paper disc diffusion method and reference antibiotic discs. Ethanol (80%) extracts of Myriophyllum exalbescens (activity ratio of .34 as compared to the 30 mcg chloramphenicol discs) Nymphaea tuberose (leaf: .40, stem: .45) were moderately active against S. aureus. Ethanol (80%) extracts of Carex lacustris (activity ratio of .34 as compared to the 10 mcg streptomycin discs), Nymphaea tuberose (leaf: 1.01, stem: 1.10) and Nuphar variegatum collected in Lake Minnetonka (leaf: .73, stem: .58) were active against M. smegmatis. All extracts were relatively inactive against E. coli except the water extract of Potamogeton natans where a low activity ration of .10 as compare to the 30 mcg chloramphenicol discs was indicated. Skellysolve F stem extracts of Nuphar variegatum collected in the Pine Lake and Sparganium fluctuans showed a rather distinct action against C. albicans, the activity ratio as compared to the 100 units mycostatin discs were 2.06 and 1.08, respectively. Regarding antifungal activity, ethanol (80%) extracts of Carex lacustris (activity ratio of 1.08 as compared to 5% aq. Phenol standard), Nymphaea tuberosa (stem: .72) and skellysolve F extract of Potamogeton zosteriformis (.60) were active against Alternaria sp., 80% ethanol stem extracts of Nymphaea tuberosa and Nuphar variegatum were active against F. roseum with the activity ratios of .41 and .48 respectively, as compared to the 5% aqueous phenol standard. In general, the plant pathogenic fungi are more resistant than animal pathogenic organisms toward the actions of aquatic plant extract.
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    The Effect of Abiotic and Biotic Factors, Symbiont Exchange Between Host Species, and Host Migration on Fungal Symbiont Community Composition and Diversity
    (2021-10) Watson, Monica
    Microbiomes, the ubiquitous communities of microbial symbionts residing within hosts, play important roles in host health, development, and fitness. While recent research has characterized the microbiomes of many different host species, our understanding of how environmental factors affect microbial community dynamics is still in nascent stages. In this dissertation, I investigate how biotic and abiotic environmental factors affect the diversity and composition of microbial symbiont communities within different host species. In chapter 1, I use a full factorial experimental plot design and culture-based methods to examine the effects of nutrient addition, large animal herbivore exclusion, and host tissue specificity on the fungal symbiont communities, known as endophytes, residing within the grass species Andropogon gerardii. While neither nutrient addition nor herbivore exclusion alone significantly affect the diversity or composition of culturable endophytes, in combination, nutrient addition and herbivore exclusion were associated with greater fungal symbiont diversity than found in other treatments. Further, while different host tissues harbored distinct fungal communities, diversity was greater in all plant host tissues sampled from plots with both nutrient addition and herbivore exclusion treatments. In chapter 2, using field collections and both culture- and sequence-based methods I compare fungal diversity and community composition in a migratory agricultural pest insect, Spodoptera frugiperda, its plant host, Sorghum bicolor, and soil collected beneath infested host plants. Finding fungal communities in insects were much more variable compared to fungal communities in plants and soil, I estimated contributions of these differing sources of fungal symbionts to the insect microbiome. Surprisingly, I find that insect fungal communities were more commonly attributed to other insect sources than to the plants on which they were feeding or to soil sources. In chapter 3, I examine the fungal symbiont communities in an overwintering population of S. frugiperda to the fungal symbiont of a migratory population to ask whether fungal symbiont communities differ over the course of migration. Specifically, I ask if the prevalence and abundance of entomopathogenic taxa is different in overwintering and migratory populations. In an analysis of environmental sources of insect fungal symbionts, I examined the fungal symbiont communities of plant hosts on which they feed at the overwintering and migratory sites. Fungal communities were surprisingly similar over the course of migration in insect hosts. While most fungal entomopathogens occurred in similar prevalence and abundance, there were two OTUs that were significantly different in abundance in the two states with one more abundant in overwintering populations and one more abundant in migratory populations. There was little evidence of fungal symbiont exchange between insects and plants. Together, these chapters characterize how both abiotic and biotic environmental factors affect fungal symbiont communities in plants and insects, the extent to which fungal symbionts may transmit among different hosts and ecological compartments, and how migration impacts microbial symbiont communities. This work has important implications for our understanding of the factors affecting microbial symbiont community dispersal and our ability to predict the effect of the environment on microbial symbiont communities in agriculturally significant species.
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    A High-Throughput Microfluidic qPCR Platform for the Simultaneous Quantification of Fecal Indicator Bacteria, Microbial Source Tracking Markers, and Pathogens in Surface Waters and Municipal Wastewater
    (2022-07) Hill, Elizabeth
    The contamination of water with enteric pathogens is known to result in adverse human health outcomes. Untreated recreational waters may carry an increased risk of gastrointestinal illnesses for water recreators, especially if waters are contaminated with sewage. Current recreational water quality standards are based on outdated methods that cannot pinpoint fecal sources of pollution or accurately predict the risk of pathogen infection. There is a critical need to elucidate the correlations between fecal pollution sources and pathogens in recreational waters. This study expanded upon previous work to develop a novel Microfluidic qPCR (MFQPCR) platform for the simultaneous detection of microbial source tracking (MST) markers, fecal indicator bacteria (FIB), and pathogens in a single water sample. Eighty previously validated TaqMan probe-based assays were applied for use in 96.96 and 192.24 GE chips from Fluidigm. Results showed that 71 of these assays were capable of quantifying genes within acceptable qPCR quality criteria with uniform concentrations and cycling conditions. Multiple host-specific MST markers, FIB, and pathogens were quantified in wastewater influent and effluent, surface waters, and fecal samples. While virulence factor genes and pathogenic species were infrequently detected, a few significant relationships were observed between pathogens and human MST markers. By these associations, linear regression models were generated to estimate the occurrence of Mycobacteria spp. from MST marker quantities and additional physicochemical parameters. This MFQPCR technology is a promising tool for amassing comprehensive pathogen datasets. Downstream applications of these data, including Quantitative Microbial Risk Assessment, may be highly impactful in the development of strategies for more accurate and timely water quality monitoring.
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    Occurences and Temporal Dynamics of Pathogens and Antibiotic Resistance Genes in Different Stormwater Reuse Systems
    (2021-12) Walsky, Tamara
    Stormwater is increasingly considered as an alternative water source for both potable and non-potable uses. However, stormwater has not been widely used as an alternative water source, primarily due to a lack of knowledge about the presence and risks associated with pathogens and antibiotic resistance genes present in raw and treated stormwater and how these populations change with environmental conditions. In my thesis research, five different stormwater reuse systems (SRS) in the Twin Cities metro area were sampled from every three weeks from June to October 2019 to build a comprehensive data set for analysis of temporal dynamics of pathogens and metal and antibiotic resistance genes (MRG/ARG) in raw and treated stormwater samples. As a follow up, two sites were time intensively sampled (i.e., sampled every 20-40 minutes as the SRS ran and water flowed through to irrigate fields) twice in summer 2020, along with tap water and lake water control sites. Microfluidic qPCR, a high-throughput quantification tool provided microbial data for 23 bacterial pathogens, 11 viral pathogens and 48 MRG/ARGs along with physiochemical testing such as turbidity, free and total chlorine, and water temperature to evaluate environmental conditions. Correlations between pathogen and MRG/ARG levels and environmental parameters such as temperature and precipitation assess the impact of precipitation and other environmental variables on pathogen and MRG/ARG concentrations in stormwater both over the season (2019 research) and during an average run where hundreds to thousands of gallons of water may be used (2020 research.) Viral and bacterial pathogens were sporadically detected both years while MRG/ARGs were widely detected. Environmental variables loosely correlated along known patterns with Fecal Indicator Bacteria (FIB) but did not account for any variation and lack of distinguished patterns seen in the data. The system with UV treatment and the system with a ball and bag filter sufficiently eliminated E. coli and limited the concentrations of MRG/ARG/pathogen genes, whereas the chlorinated system did not. SRS without any microbial treatment had no effect on cultured FIB and concentrations of MRG/ARG/pathogen genes. These results will provide previously unknown information crucial to successful expansion of stormwater reuse, especially for uses with greater human exposure.
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    Soil microbes drive the classic plant diversity–productivity pattern
    (Ecological Society of America, 2011) Schnitzer, Stefan A; Klironomos, John N; HilleRisLambers, Janneke; Kinkel, Linda L; Reich, Peter B; Xiao, Kun; Rillig, Matthias C; Sikes, Benjamin A; Callaway, Ragan M; Mangan, Scott A; van Nes, Egbert H; Scheffer, Marten
    Ecosystem productivity commonly increases asymptotically with plant species diversity, and determining the mechanisms responsible for this well-known pattern is essential to predict potential changes in ecosystem productivity with ongoing species loss. Previous studies attributed the asymptotic diversity–productivity pattern to plant competition and differential resource use (e.g., niche complementarity). Using an analytical model and a series of experiments, we demonstrate theoretically and empirically that host-specific soil microbes can be major determinants of the diversity–productivity relationship in grasslands. In the presence of soil microbes, plant disease decreased with increasing diversity, and productivity increased nearly 500%, primarily because of the strong effect of density-dependent disease on productivity at low diversity. Correspondingly, disease was higher in plants grown in conspecific-trained soils than heterospecific-trained soils (demonstrating host-specificity), and productivity increased and host-specific disease decreased with increasing community diversity, suggesting that disease was the primary cause of reduced productivity in species-poor treatments. In sterilized, microbe-free soils, the increase in productivity with increasing plant species number was markedly lower than the increase measured in the presence of soil microbes, suggesting that niche complementarity was a weaker determinant of the diversity–productivity relationship. Our results demonstrate that soil microbes play an integral role as determinants of the diversity–productivity relationship.