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Browsing by Subject "Fungi"

Now showing 1 - 9 of 9
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    Borosin foray: Expanding a family of fungal autocatalytic α-N-methylating RiPP natural products
    (2020-07) Quijano, Marissa
    Backbone N-methylations impart several favorable characteristics to peptides including increased proteolytic stability and membrane permeability. Nonetheless, amide bond N-methylations incorporated as post-translational modifications are scarce in nature and were first demonstrated in 2017 for a single set of fungal metabolites. Here we expand on our previous discovery of iterative, autocatalytic α-N-methylating precursor proteins in the borosin family of ribosomally encoded peptide natural products. We identify over 50 putative pathways in a variety of ascomycete and basidiomycete fungi and functionally validate nearly a dozen new self-α-N-methylating catalysts. Significant differences in precursor size, architecture, and core peptide properties subdivide this new peptide family into three discrete structural types. Lastly, using targeted genomics, we link the biosynthetic origins of the potent antineoplastic gymnopeptides to the borosin natural product family. This work highlights the metabolic potential of fungi for ribosomally synthesized peptide natural products.
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    Discovery and characterization of sesquiterpenoid biosynthetic pathways from Basidiomycota
    (2014-01) Wawrzyn, Grayson Thomas
    Terpenoids are the largest group of secondary metabolites and can be found in organisms ranging from microscopic bacteria to large plant species. These compounds are commonly used for signaling and defense against ecological predators/competitors and possess many unique and interesting biological activities. Many compounds possess enough value that large scale production of terpenoids for biofuel (e.g. farnesene) and pharmaceutical (e.g. artemisinin) applications are well underway. The goal of this work was and still is to uncover the biological machinery responsible for making the bioactive terpenoid compounds. This requires a deep understanding of the underlying biochemistry as well as the genetic organization of the organism from which you are trying to extract said machinery. In the context of this research the biosynthetic machinery is the enzymes (primarily sesquiterpene synthases and P450 monooxygenases) responsible for synthesizing the anticancer illudin terpenoids, and the target organism is the fungus Omphalotus olearius. To accomplish this goal I identified the first biosynthetic pathway enzyme, a protoilludene synthase, and identified putative modifying enzymes that catalyze further modification of the first pathway intermediate. Arguably more importantly, I chose to use our biochemical data to better understand sesquiterpene synthases across many fungal genera. This work provides significant breakthroughs in understanding illudin biosynthesis and also provides a predictive framework for further examination of terpenoid biosynthesis in many different fungal species.
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    Evaluation of Endophytic Beauvaria bassiana as a Targeted Insecticide in Tomato
    (2015-09) Pai, Shantal; Bushley, Kathryn
    A targeted insecticide treatment has great value in agriculture because it would mitigate insect damage while causing no harm to non-harmful insects, especially pollinators. Beauvaria bassiana is an endophyte which has been shown to improve plant growth and is a known insect pathogen. It was hypothesized that the combination of these two traits would make B. bassiana a potential targeted insecticide. Two tomato (Solanum lycoperscicum) varieties, Early Girl and Heinz 1706-BG, were inoculated with Beauvaria bassiana. The Early Girl variety was tracked to assess plant-fungal interactions, while the Heinz variety was inoculated with beet armyworm larvae (Spodoptera exigua) to examine effects of Beauveria on herbivory. Our results show that B. bassiana was transferred from the leaf tissue to the beet armyworm larvae, infecting and killing some insects, and slowing insect damage. Our results also show some indication that B. bassiana of pathogenic, rather than mutualistic, interaction with the Early Girl variety of tomato.
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    Fungi in Antarctica: a circumpolar study of biodiversity in soils and historic structures.
    (2010-07) Arenz, Brett Evan
    Antarctica is the most remote and isolated continent on Earth and is generally thought to have low biodiversity due to environmental extremes. These relatively simple ecosystems are important to study because they can be used to improve understanding of more complex systems world-wide that are difficult to analyze directly. The isolation of the continent, extreme environmental conditions and the lack of functional redundancy in ecosystem processes make it particularly vulnerable to human disturbance and require improved understanding. The results of this research support the hypothesis that fungal abundance and distribution are generally linked to the presence of primary producers and their effect on carbon and nitrogen quantities in the soil. Experiments introducing sterile plant-derived nutrient sources (wood and cellulose) to soils resulted in increased fungal abundance up to three to four orders of magnitude greater than background soil levels. This suggests that the extremes of the Antarctic environment (low moisture, high salinity, cold temperatures) are primarily affecting fungi by limiting the distribution of flora and direct effects on the fungi are relatively less important as these indigenous soil fungi appear well adapted to Antarctic environment. A survey of fungal diversity near historic sites and areas where materials were introduced to the Antarctic Peninsula reveals a very similar composition to those affecting historic sites on Ross Island. The fungi found in greatest abundance were species of Geomyces and Cadophora. These two genera also formed a large percentage of the fungal colonization of buried nutrient substrates. The frequent reports of these fungi from many areas in Antarctica and the large diversity of species found indicates they are well adapted to their environment and suggests they are indigenous to Antarctica. The dominance of these fungi on human-introduced material indicates direct human influences may be of more benefit to generalist indigenous decomposer fungi which are pre-adapted to the environmental extremes rather than human-introduced fungi which may be better adapted to utilizing these substrates but not well adapted to the Antarctic environment. It also supports the hypothesis of indigenous Antarctic fungi being primarily limited by nutrient availability.
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    A history of both clonality and recombination governs the population structure of Alternaria endophyte communities on prairie Dalea
    (2021-10) DeMers, Mara
    Prairie has become one of the most endangered biomes in North America under changing climates engendered by anthropogenic activity. The patterns of diversity we observe of native prairie species in remnant prairie sites are the outcome of both historical and contemporary processes, and understanding these underlying processes will inform the responses of these populations to future environmental changes. The assembly of fungal endophyte communities within plants depends on the complex interactions of fungal taxa, their host plants, and the abiotic environment. Prairie plant communities provide a unique avenue to explore the interplay of biotic and abiotic factors affecting endophyte communities, since the historical distribution of prairies spans a broad range of temperature and precipitation, while the distances between small fragments of contemporary prairie communities may challenge the dispersal capabilities of these otherwise ubiquitous fungi. We sampled foliar fungal endophytes from two native prairie legumes, purple and white prairie clovers (Dalea purpurea and D. candida), in 17 remnant prairie sites across Minnesota in order to evaluate the relative contributions of abiotic factors, host species, and dispersal limitation to the diversity and structure of these communities. We found that similarity of communities was significantly associated with their location along a temperature and precipitation gradient, and we showed a distance-decay relationship that suggests dispersal limitations only over very large spatial scales. Although the effect of host species was small relative to these other factors, the two Dalea species maintained distinct communities within sites where they co-occur. Our results illustrate the capacity of many of these endophyte taxa to disperse over large distances and across heterogeneous biotic and abiotic environments and suggest that the interplay of biotic and abiotic factors maintains high diversity observed in endophyte communities. Our results showed that community composition of endophytic fungi in Dalea spp. varied along a precipitation and temperature gradient, among hosts, and in apparent response to the abundance of Alternaria spp., but left unexplained patterns of genetic variation among the many isolates assigned to Alternaria alternata. We used genotyping-by-sequencing (GBS) to assess population genetic structure of endophytic Alternaria among sampling sites and between host species, and compare levels of recombination and clonality and assess evidence for sexual or parasexual reproduction in these communities. We found cryptic diversity among sequenced samples, as only a subset aligned well to A. alternata reference genomes. Analysis of sequences closely related to reference A. alternata genomes, treated here as a single species, revealed a high level of clonality, and genotypic diversity shared across populations. However, we also detected evidence of recombination events consistent with sexual or parasexual reproduction, as well as two mating types, MAT1-1 and MAT1-2, which were present in roughly equal frequencies in all but one sampled population. Together, the results suggest recent asexual proliferation after rapid colonization of the sampled sites from an ancestral source population. Recombination likely occurred more frequently in the source population, and is now rare.
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    An Interdisciplinary Geochemical and Genomics Approach to Understanding Fungal Selenium Transformations for the Bioremediation of Contaminated Waters
    (2021-07) Sabuda, Mary
    Selenium (Se) is both a micronutrient required for most life and an element of environmental concern due to its toxicity in high concentrations. Se can be released into the environment through both natural and anthropogenic (human) activity, where it can exist as volatile or organic Se(-II), nanoparticulate Se(0), or aqueous Se(+IV/VI). Coal mining, processing, and burning can release high levels of Se to the environment, as selenium can easily substitute for sulfur, a main component of coal. Se is also useful in the medical field, where it has anticancer properties and Se(0) is an effective coating on medical devices. While most knowledge of biotic Se transformations is related to either anaerobic or aerobic bacterial processes, some common soil Ascomycota fungi can reduce Se under oxic conditions. These microeukaryotes readily transform elevated concentrations of this essential toxin from a bioavailable aqueous phase (Se(IV/VI)) to solid or volatile phases (Se(0/-II)), which is ideal for engineering efficient, cost-effective treatment strategies for Se-contaminated environments. Elucidating the geochemical and genetic mechanisms behind filamentous fungal Se transformation strategies will progress biotechnological applications for biogenic Se nanoparticles, and aid in a more complete understanding of Se biogeochemical cycling.
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    Investigations of Potential Plant Pathogens in Forests and Nurseries in Minnesota and Fungal Diversity studies in the Ecuadorean Amazon
    (2024-07) Rajtar, Nickolas
    Plant pathogens pose significant threats to natural ecosystems and managed landscapes, leading to substantial economic losses and ecological damage. Despite their potential impact, there remains a gap in comprehensive biosurveillance to monitor and understand the distribution and diversity of these pathogens. This dissertation addresses this gap through three biosurveillance projects focusing on detecting and describing canker fungi associated with emerald ash borer in Minnesota, the distribution and diversity of Phytophthora species across environments in Minnesota and the diversity and decay potential of Xylaria species in the Ecuadorian Amazon Rainforest. Chapter 1 investigates the pathogenicity of canker fungi associated with emerald ash borer (EAB)- infested ash trees in Minnesota. The study focuses on seven fungal species isolated from EAB galleries and tests their potential to cause cankers in white ash (Fraxinus americana). The pathogenicity of these fungi was tested using two inoculation methods, and the results demonstrated that several fungi, particularly Diplodia mutila, Cytospora pruinosa, and Diplodia seriata, cause significant canker formation. This research underscores the potential role of these fungi in exacerbating the decline of ash trees affected by EAB. Chapter 2 presents a survey of Phytophthora species in Minnesota, examining their presence across various built and natural environments including nurseries, forest stands, and waterways. This study expanded upon previous Phytophthora surveillance activities which had been limited in geographic scope, and which had predominantly sampled diseased plant material from nurseries. Over four years, soil, plant, and water samples were collected from nurseries, forest stands and urban landscapes. The survey identified 22 distinct Phytophthora species, including 14 previously unreported in Minnesota. The findings highlight the diversity of Phytophthora species in Minnesota and emphasize the need to monitor nurseries as a potential source of entry for new, and potentially hazardous, species to the state. Chapter 3 explores the diversity and decay potential of Xylaria species in the Ecuadorian Amazon Rainforest. Through extensive field collections and laboratory analyses, the study identified numerous Xylaria species, many of which (60 within a one hectare area) were previously undescribed. The decay potential of selected Xylaria species was assessed on various wood types, revealing significant biomass loss and indicating their role in nutrient cycling within the rainforest ecosystem, in particular trees that are high in extractives and regarded as being resistant to decay. This research presents critical new information on the presence and impact of plant pathogens and diverse fungi in Minnesota and the Ecuadorian Amazon. It highlights the importance of biosurveillance for understanding plant pathogens, pests, beneficial organisms and their interactions and implications for forest health and ecosystem dynamics. These findings contribute to the broader field of plant pathology and provide valuable insights for detecting, mitigating and managing the impact of plant pathogens.
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    Prospecting Fungi For Methane Biofiltration Reveals High-Efficiency Capture By Dried Mycelia (Necromass)
    (2017-12) Liew, Feng Jin
    Fungi can improve biofiltration of hydrophobic pollutants by improving capture, a rate-limiting step in bioreactors. We prospected fungi alongside native biofilm preparations and relevant controls for their efficacy capturing methane using gas-phase biofilters. Using a batch incubation system, we found that Ganoderma lucidum performed best in single-strain trials. Building on this, we tested other Ganoderma species and found comparable efficacies. The advantages of Ganoderma and Pleurotus isolates were lost and native colonizers wood substrates were deployed in the field, irrespective of where they were deployed. This relates to a stress-tolerant rather than competitive life history strategy, where Ganoderma species are outcompeted in less stressful environments. We also tested an alternative way to present Ganoderma for filtration. Using protocols for culinary and biomaterial applications, we re-tested several fungi, including Lentinus edodes ‘shiitake.’ In these trials, we found surprisingly high efficacy with Ganoderma mycelia (84%) relative to activated carbon. These results suggest that Ganoderma species might best be utilized for biofiltration in dried form, effective in field conditions and potentially more amenable for biofiltration indoors.
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    Role of Fungi in the Biofiltration of Livestock Housing and Manure Storage Emissions
    (2015-08) Oliver, Jason
    Biofilters use porous media colonized by microbial biofilms to capture and degrade odorous, hazardous and greenhouse gases making them well-suited for livestock housing and manure storage emissions. Fungi are abundant in these biofilters though their dynamics, degradation of media, community shifts, and functional roles have not been well-investigated. To explore spatial and temporal fungal dynamics in full-scale woodchip biofilters treating swine barn emissions, a novel monitoring approach was developed. Using wooden baits and microbial measures optimized to target biofilms biofilter fungi were characterized and shown to tolerate media desiccation. Additionally, successional patterns at the taxa and guild level were studied, and the development of a dominant fungal community was identified. To address the practical question of media longevity, a litter bag study was deployed in the same full-scale biofilters. Decay rates of various media types were identified, and microbial decay was dependent on media quality, nitrogen, and emissions levels. Using a lab-scale biofilter system, fungi were shown to improve the capture of methane, particularly after periods of low-concentration inlet emissions. Using a chromatographic isotherm the ability of fungi to sorb methane gas was verified for the first time. Collectively, this work showcases dynamics and potential abilities of fungi in biofilters treating livestock production emission and may be used to guide subsequent efforts to connect fungi to biofilter function. If these processes can be understood and controlled, there is the potential to improving biofilter performance, better protect air quality and improve farming system sustainability.