The impact of fungal volatile organic compounds on yeast

This project seeks to understand how the presence of certain fungi and the specific volatile organic compounds (VOCs) that they produce can influence the community of microbes in a confined space such as the built environment. VOCs are gaseous at room temperature, readily dissipate throughout the environment, and often function as signaling molecules. This dissertation investigates how commonly emitted fungal VOCs influence the growth and metabolism of yeast (Saccharomyces cerevisiae) in a shared space.A method was developed to evaluate Saccharomyces cerevisiae as a model for screening the effects of volatile organic compounds and the impact of 27 VOCs on yeast growth was determined. In this VOC screen, gas-phase formaldehyde, three common fungal VOCs, 1-octanol, 1-octen-3-one, and trans-2-octenal, and a common plant VOC, trans-2-hexen-1-al, completely inhibited yeast growth at 10 ppm, while 1-octen-3-ol, 2-methylpropanal and benzene were significantly limiting. Additionally, 2 common fungal VOCs, 3-methyl-1-butanol and 3-octanone, significantly increased yeast growth.To begin to investigate the mechanism of action of specific VOCs, I reanalyzed data from a previously conducted genome-wide screen to a lethal concentration of 1-octen-3-ol, which found that when endosomal sorting pathways are disrupted, yeast is resistant to 1-octen-3-ol. I then conducted a genome-wide screen using a lethal concentration of another C-8 volatile, 1-octanol, which identified the endomembrane as a key gene category that conferred resistance. Two genome-wide screens with sublethal concentrations of 1-octen-3-ol and 1-octanol were also conducted to identify the genes and pathways involved in sensitivity to these VOCs, and both of those screens identified all the genes in the tryptophan biosynthetic pathway. The retromer complex was identified as the most significantly over-represented cellular component among the sensitive mutants to 1-octanol, and 2 retromer mutants were also sensitive to 1-octen-3-ol, though not significantly overrepresented in the gene set. I then conducted follow-up studies using tryptophan supplementation in the media and found that additional tryptophan rescued the sensitive mutants when exposed to inhibitory VOCs.