Browsing by Subject "Fungal"

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    Distribution of mycotoxins in fungal structures
    (2011-06) Errede, Dawn C.
    Exposure to mycotoxins associated with small fungal fragments may cause adverse health effects. Current air sampling methods may not detect such fragments and may cause researchers to underestimate fungal exposures. Understanding how time and substrate affect the distribution of toxins and their release into the environment can strengthen estimates of potential risks of exposure to these toxin-carrying particles. This research investigated the influence of time and growth substrate on the amount and distribution of mycotoxins in fungal structures and particles released from the fungal colonies. A common, toxin-producing, indoor mold, Aspergillus versicolor, was inoculated on two different agars: Malt Extract (MEA) and Wallpaper Paste (WPA). Fungal material was collected both by coring the plates, and by washing the plates with sterile water and glass beads at weekly intervals from one to six weeks. The wash water suspensions were filtered through 20- and 1-micron filters and lyophilized. The filters and the lyophilized wash water samples were extracted with methanol and analyzed for both sterigmatocystin and ergosterol (a marker of fungal growth). Results indicate that overall growth and toxin levels are higher on MEA than on WPA, but when standardized against ergosterol, sterigmatocystin levels on WPA are higher. Measurable amounts of ergosterol and sterigmatocystin are detectable in the lyophilized wash water. Ergosterol and sterigmatocystin increase steadily over six weeks on WPA, but peak around 3-4 weeks on MEA. Our conclusions are that small fungal fragments can carry toxins at levels that could deliver biologically significant doses if the fragments were inhaled into the deep lung.
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    Drivers of root and fungal litter decomposition: implications for soil carbon cycling
    (2021-05) See, Craig
    Globally, soils contain more carbon (C) than vegetation and the atmosphere combined. Despite clear importance to the global C budget, estimates of C fluxes into and out of soils remain highly uncertain. Decomposition is the dominant process by which C is lost from soil, but most of what is known about the controls of this process comes from studies of leaf litter at the soil surface. My first two chapters explore factors affecting the decomposition of two common belowground litter types. Chapter one is a global meta-analysis of the drivers of fine root decomposition, and is the first to explore the effects of species-level traits in addition to climate and substrate chemistry. My second chapter describes an experiment characterizing the dynamics and chemical drivers of fungal necromass decomposition, an important and understudied flux of soil C. My final chapter focuses on the role of soil fungi in the formation of “stabilized” soil C in the form of mineral associated organic matter (MAOM). Here, I call into question the current assumption that new MAOM formation in soil occurs in close proximity to root surfaces. Using quantitative estimates of fungal exploration, I put forth the hypothesis that fungal hyphae play an underappreciated role in distributing C through soil, and that hyphal contact with minerals encourages the formation of MAOM. This work suggests that current potential for MAOM formation in soils is significantly underestimated by not accounting for the impact of fungi.