URochester Evolutionary Biologist Dr. Justin Fay conducted an investigation into how yeasts tolerate higher temperatures due to global warming in fall of 2025. The Fay Lab is a culmination of undergraduate and graduate students comparing the genomes of two different species of yeasts in the genus Saccharomyces — S. cerevisiae and S. uvarum. Saccharomyces is known for their fermenting abilities and is used in the Fay lab to understand how some organisms can tolerate heat more effectively than others. Studying model organisms such as yeasts convey a great deal of information about how life adapts to rising temperatures from global warming today.
Graduate students, including PhD candidate Nasima Akhter, played an active role in analyzing yeasts’ adaptations. “My main role was to design and carry out experiments and analyze the data, combining both hands-on lab work and computational analysis,” Akhter said. “By studying how different Saccharomyces yeast species respond to heat at the molecular level, I’m working to understand how heat tolerance has evolved.”
“The big difference between these two species [S. cerevisiae and S. uvarum] is their ability to survive at different temperatures,” Fay explained.
To determine which yeast species can withstand higher temperatures, they collaborated with biologist Dr. Sina Ghaemmaghami’s lab and URMC biochemist Dr. Eric Phizicki’s lab to perform thermal proteomic profiling on the specimens. Ghaemmaghami’s lab noted how joining Fay’s project was a key opportunity to expand their knowledge of protein function at the genetic level.
The Ghaemmaghami lab centers their study on proteomics, which narrows their focus more on the detailed molecular structure and functions of protein. However, collaborating with the Fay lab gave them the opportunity to “zoom out” and think of proteins in the broader context of the whole organism. “By integrating proteomics with evolutionary and genetic analyses, we were able to see that changes in protein folding stability and degradation pathways can influence how yeast populations adapt to environmental stress, such as high temperature,” Ghaemmaghami described. “The work provided new insight into how fundamental biochemical processes can evolve and, in doing so, help organisms survive and thrive in challenging conditions.”
The procedure included proteins being extracted from yeast exposed to high temperatures. Their stability was assessed by measuring whether they remained soluble and properly folded. S. cerevisiae tolerated temperatures of about 8°C higher than S. uvarum. About 85% of proteins involved in determining heat resistance, also known as thermotolerance, in S. cerevisiae stayed stable and continued folding under heat stress, while the corresponding proteins in S. uvarum degraded.
Furthermore, the biologists determined that factors besides protein structure, such as other proteins and molecules in the local cellular environment, influence thermotolerance in these yeasts. The researchers discovered this by breeding individual S. cerevisiae and S. uvarum specimens to create a hybrid yeast. After exposing the hybrid sample to high temperatures of 70°C, they determined that the heat-sensitive proteins in hybrid yeast were more resistant to higher temperatures. This finding shed light on how yeast did not rely on solely proteins to achieve thermotolerance, but recruited other molecules and “heat shock chaperone” proteins to adjust chemical conditions to withstand these higher temperatures.
“If an organism wants to increase its thermal tolerance, you want to be able to survive at two degrees higher or three degrees higher,” Fay said.
The results from the project show that organisms must change the entirety of the proteins they encode in their genomes to increase their tolerance. This promotes heat resistance so they can survive in their environments as efficiently as possible, also described as having “a strong evolutionary constraint.”
This study is a major advancement in Fay’s studies and was supported by a $1.8 million grant from the National Institute of Health. Fay and his fellow researchers will continue investigating heat resistance in different organisms, studying both genetic and protein analysis to understand the genetic changes that allow for heat resistance.
For students such as Akhter, the most rewarding aspects of taking on this project were developing their skills in laboratory research itself and solving complicated problems, along with a deeper understanding of the biologies of model organisms such as yeasts.
“I learned … how to explore multiple ways to approach a research problem [instead of being stuck on one idea],” Akhter said. “I also learned how to narrow down possibilities and decide the best next steps in research. … Being part of a collaborative lab and getting helpful feedback from Justin [Fay] and the team has greatly guided the direction of my [role in this] project.”
