Date of Award
Honors College Thesis
Kevin A. Kuehn, Ph.D.
A growing body of evidence has emerged over the last several decades on the usefulness of the fungal sterol, ergosterol, in quantifying fungal biomass within decaying plant litter and the technique for measuring instantaneous growth rates of fungi via rates of [14C]-acetate incorporation into ergosterol. Although popular, an underlying problem with these methods is the paucity of studies that have determined conversion factors that relate the precursor molecules to meaningful measurements of fungal biomass and growth rates, respectively. This research was conducted to establish conversion factors relating rates of 14C-acetate incorporation to rates of fungal mass synthesis. Sterile leaf litter pieces of J. effuses were inoculated with one of three fungal species (Drechslera sp., Marasmiellus sp. or Panellus copelandii) and harvested periodically over 20-25 days to estimate the rate of fungal mass increase (via ergosterol). Additional litter pieces were also harvested at intermediate times in order to estimate rates of [1-14C]-acetate incorporation into ergosterol. Conversion factors were calculated as: the specific rate of fungal mass produced (µg h-1) based on ergosterol divided by the amount of acetate incorporated (nmol h-1). Significant increases in ergosterol (p<0.001) were observed in litter pieces during the incubation period. Calculated conversion factors among the fungal isolates examined were significantly different (p = 0.011), ranging between 19.6±2.8 and 47.2±4.9 µg fungal mass nmol-1 acetate incorporated. Overall, our estimated conversion factors are slightly higher than the range reported for other fungal species isolated from decaying plant litter. As a consequence, greater elucidation of specific conversion factors for both ergosterol to fungal mass and 14C-acetate to fungal growth rates are clearly needed in order to decrease the existing uncertainty in ergosterol-based methods.
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Harrell, Jakayla M., "Determination of 14C-acetate incorporation to fungal mass conversion factors of selected saprophytic fungal organisms" (2013). Honors Theses. 149.