fermentations Yeast fermentations in the lab. Photo courtesy of Kaitlin Fisher.

MMI Fellow seeks to understand sugar production in yeasts

Kaitlin Fisher, Morgridge Metabolism Interdisciplinary (MMI) Fellow, focuses her research around the absence of genes necessary for gluconeogenesis—the metabolic pathway that synthesizes glucose sugar—in a genus of non-model budding yeasts, Hanseniaspora. She seeks to determine if these particular yeasts have a radically different carbon metabolism from most other organisms that do not perform gluconeogenesis, or if they simply produce glucose differently. 

The MMI Fellowship is a graduate fellowship launched in 2018 by the Morgridge Institute for Research with the hope of bringing “fresh eyes” to the growing pursuit of metabolism research at UW–Madison.

Kaitlin Fisher
Kaitlin Fisher

“Katie is doing some really innovative research on an understudied group of yeasts with streamlined metabolism,” says Chris Hittinger, associate professor of genetics at UW–Madison. “They have either discarded biochemical pathways present in nearly all free-living organisms or invented new ways of doing them. The answer could even be both, but either way, she is going to discover something very interesting when she gets it solved.”

Fisher, whose background is in the study of evolutionary biology, was named the 2020 MMI Fellowship awardee last September, when she began her work in the Hittinger Lab to approach the subject of carbon metabolism in yeasts from a genetic point of view. In other words, her research aims to find the genes that underlie the unique carbon metabolism of the Hanseniaspora yeasts. 

“The yeasts you are most familiar with are Saccharomyces cerevisiae, the yeast you use to bake your bread and brew your beer,” Fisher says. “But there are over a thousand unique species of budding yeasts and most of them would be pretty terrible at brewing beer but they have other really cool and really interesting characteristics.” 

Hanseniaspora have undergone a remarkably reductive genome transformation, meaning through evolutionary time, they have lost a lot of genes. Reduction in genomes is not uncommon, according to Fisher, but the specific genes and the frequency of the loss are surprising to most geneticists. The genes that are being lost are genes that most biologists consider to be important, leading scientists like Fisher to question how these organisms’ function without them. 

“The personnel through the Morgridge Metabolism Initiative have been really useful, because there are definitely approaches and techniques that I’m not aware of as a non-metabolism trained person; I am comfortable I can find someone who does know how to do what I need to do if I reach out,” Fisher says. “So, in that sense the community I think is a really helpful tool.” 

Since the genome sequences for Hanseniaspora are known, most scientists are interested in doing experiments at the bench, making the current COVID-19 pandemic a large barrier for their research, according to Fisher. These yeasts are difficult to work with, so new tools and new approaches need to be used to begin to do genetic experiments with them and begin to understand their genome. 

Fisher cites the collaborative nature of the Metabolism Theme at the Morgridge Institute as the reason for her ability to transition into the metabolic field with ease.

“Morgridge has a number of venues for collaborative meeting and of course COVID-19 has really changed that and changed the landscape for research at UW–Madison,” Fisher says. “But prior to that the collaborative meetings that Morgridge has, especially the Morgridge Metabolism Initiative, have been really useful.”