Searching for Novel Killer Yeasts from the Palouse
Additional Funding Sources
The project described was supported by a student grant from the UI Office of Undergraduate Research.
Abstract
Killer yeasts are strains of yeast that take their name from their ability to produce antifungal toxins that are lethal to a variety of other fungi, including human pathogens. Killer yeasts are potentially important to medicine because they may provide insights for the development of novel drugs used to treat fungal infections. Our objective is to identify new toxins in 48 wild yeast isolates that the Rowley lab has collected from produce at the Moscow Farmer’s Market since 2018. We assayed for killer toxin production by competing putative killer yeasts against different species of fungi on agar plates. If found to be a producer of killer toxins, a zone of growth inhibition is formed around the yeast. This can be seen if there is a circular halo shown, representing cell death. While other fungi showed little to no susceptibility, it was discovered that Pichia pastoris (SMD1168H) was susceptible to killer toxins produced by 9 of the yeasts. Most killer toxins are encoded by double-stranded RNA (dsRNA) viruses called satellites. To determine if the killer yeasts identified contained satellites, dsRNAs were extracted from each identified killer yeast. No relationship was found between the presence of dsRNAs and killer toxin production. This work validated our approach to identifying novel killer toxins isolated from the Palouse.
Searching for Novel Killer Yeasts from the Palouse
Killer yeasts are strains of yeast that take their name from their ability to produce antifungal toxins that are lethal to a variety of other fungi, including human pathogens. Killer yeasts are potentially important to medicine because they may provide insights for the development of novel drugs used to treat fungal infections. Our objective is to identify new toxins in 48 wild yeast isolates that the Rowley lab has collected from produce at the Moscow Farmer’s Market since 2018. We assayed for killer toxin production by competing putative killer yeasts against different species of fungi on agar plates. If found to be a producer of killer toxins, a zone of growth inhibition is formed around the yeast. This can be seen if there is a circular halo shown, representing cell death. While other fungi showed little to no susceptibility, it was discovered that Pichia pastoris (SMD1168H) was susceptible to killer toxins produced by 9 of the yeasts. Most killer toxins are encoded by double-stranded RNA (dsRNA) viruses called satellites. To determine if the killer yeasts identified contained satellites, dsRNAs were extracted from each identified killer yeast. No relationship was found between the presence of dsRNAs and killer toxin production. This work validated our approach to identifying novel killer toxins isolated from the Palouse.