Dr. George van der Merwe

My interest in yeast molecular and cellular biology started during my undergraduate years at the University of Stellenbosch in South Africa. I graduated with a B.Sc. (Microbiology) and enrolled in graduate studies with the focus on understanding the regulation of nitrogen metabolism in Saccharomyces cerevisiae, the commonly used brewer's and wine yeast. These studies allowed me to complete parts of my Ph.D. at the University of Tennessee (Memphis), Brock University (CCOVI), and the University of British Columbia (WRC). As a Research Associate at the University of British Columbia I developed an interest in the adaptation of yeast to fermentation-related stresses. Since joining the University of Guelph in 2002, my research focussed on understanding the molecular responses of yeast to its environment. We use standard microbiology, molecular biology, cellular biology, and genetic techniques as well as advance tools such as genomics and metabolomics to unravel the yeast's adaptation to environmental changes. We apply this information to fermentation industries (wine, beer and cider production). Research performed in my laboratory is funded by Natural Sciences and Engineering Research Council of Canada (NSERC), Genome Canada, Ontario Genomics Institute, the Agricultural Adaptation Council, and the Ontario Ministry of Agriculture, Food and Rural Affairs.

• B.Sc: University of Stellenbosch
• Ph.D.: University of Stellenbosch
• Research Associate: University of British Columbia

Yeasts are confronted with an array of challenging conditions in its natural environment and during commercial fermentation processes. In both instances the yeast have to cope with fluctuating nutrient availability, osmotic stress-inducing concentrations of sugars, varying temperatures, and increasing concentrations of ethanol and organic acids. The molecular adaptations to these environments include genomic, transcriptomic and proteomic adjustments to ultimately facilitate metabolic and physiological adaptations that enable growth and survival. My laboratory focuses on understanding the molecular mechanisms that: (1) enable the adaptation of yeast to fermentation-related stresses, and (2) link molecular adaptation and metabolite production. Knowledge generated from this research would enable us to devise strategies to improve the stress tolerance, vitality, and efficiency of yeast during its performance of alcoholic fermentations.

Adaptation to changing nutrient environments

Yeasts consume nutrients, including fermentable sugars and nitrogen sources, to produce biomass and metabolites, such as ethanol, organic acids and flavour compounds, during the fermentation process. S. cerevisiae employs an intricate network of regulatory proteins that adjusts its transcriptome and proteome in response to prevailing nutrient conditions. Despite decades of research to understand the nutrient adaptation of yeast, many questions remain unanswered. We have identified an E3 ubiquitin ligase, the Vid30 or GID (Glucose Induced degradation Deficient) complex, as a novel component on the regulation of the transcriptomic and proteomic adaptation of yeast to changing nutrient conditions. The intricacies of Vid30c’s role in nutrient regulation remain unresolved. Elucidating its mechanism of function in nutrient adaptation will not only increase our fundamental understanding metabolic regulation in eukaryotic cells, but also increase our understanding of the continuous nutrient depletion yeasts experience during fermentation.

Yeast domestication and fermentations

Yeasts evolve to adapt to its specific environment. Brewer’s yeasts have been selected over centuries of fermentations to perform specific functions to satisfy the needs of brewers. This domestication is rooted in genomic adaptations that developed desired traits, like increased maltose metabolism, flocculation and tolerance to fermentation stresses, and omitted undesirable traits, like the ability to produce unwanted phenolic off flavours. There are several aspects of yeast domestication that remain unresolved. Unraveling

the origins and molecular underpinnings of domesticated traits will increase our understanding of yeast performance thereby developing strategies and predictions of fermentation efficiencies and flavour compound production during alcoholic fermentations (e.g. beer, cider, sparkling wine production).

Yeast diversity

While species of the genus Saccharomyces are commonly used in alcoholic fermentations, several non-Saccharomyces yeasts produce unique flavour compounds thereby adding flavour complexity and expanding product diversity in the wine, beer and cider industries. For example, strains of the yeast Brettanomyces bruxellensis are commonly employed in Belgian-style beers and are increasingly used in either primary or secondary fermentations in North American beer production. Understanding the contributions of these yeasts to flavour complexity will allow the development of strategies to increase product diversity in the beer and cider industries.

• Caroline Tyrawa, Richard Preiss, Meagan Armstrong, and George van der Merwe. (2019) The temperature dependent functionality of Brettanomyces bruxellensis strains in wort fermentations. J. Inst. Brew. 125(3): 315-325 https://doi.org/10.1002/jib.565
• Richard Preiss, Kristoffer Krogerus, Caroline Tyrawa, Lars Garshol, and George van der Merwe. (2018) Traditional Norwegian kveik are a genetically distinct group of domesticated Saccharomyces cerevisiae brewing yeasts. Front. Microbiol. 9:2137. https://doi.org/10.3389/fmicb.2018.02137
• Richard Preiss, Caroline Tyrawa, and George van der Merwe. (2018) Autophagy gene overexpression in Saccharomyces cerevisiae perturbs subcellular organellar function and accumulates ROS to accelerate cell death with relevance to sparkling wine production. Appl. Microbiol. Biotechnol. 102(19): 8447–8464. https://doi.org/10.1007/s00253-018-9304-y
• Jacqueline Pierce, George van der Merwe and Dev Mangroo. (2014) Protein Kinase A Is Part of a Mechanism That Regulates Nuclear Reimport of the Nuclear tRNA Export Receptors Los1p and Msn5p. Euk. Cell. Feb;13(2):209-30. doi: 10.1128/EC.00214-13
• Kyrylo Bessonov, Christopher Walkey, Barry Shelp, Hennie van Vuuren, David Chiu, and George van der Merwe. (2013) Functional Characterization of NSF1 in Saccharomyces cerevisiae During Wine Fermentation Using Interconnected Correlation Clustering and Molecular Analysis. PLoS ONE 8(10): e77192. doi:10.1371/journal.pone.0077192
• Snowdon, C., and van der Merwe, G. 2012. Regulation of Hxt3 and Hxt7 turnover converges on the Vid30 complex and requires inactivation of the Ras/cAMP/PKA pathway in Saccharomyces cerevisiae. PLoS One. 2012;7(12):e50458. doi: 10.1371/journal.pone.0050458. Epub 2012 Dec 5.
• Christopher Snowdon, Ryan Schierholtz, Peter Poliszczuk, Stephanie Hughes, and George van der Merwe. 2009. ETP1 HL010c is a novel gene needed for the adaptation of Saccharomyces cerevisiae to ethanol. FEMS Yeast Res. 9:372-380.
• Chris Hlynialuk, Ryan Schierholtz, Amanda Vernooy, and George van der Merwe 2008. Nsf1p/Ypl230wp participates in transcriptional activation during non-fermentative growth and in response to salt stress in Saccharomyces cerevisiae. Microbiology 154:2482-2491.
• Chris Snowdon, Chris Hlynialuk, and George van der Merwe. 2008. Components of the Vid30c are needed for the rapamycin-induced degradation of the high-affinity hexose transporter Hxt7 in Saccharomyces cerevisiae. FEMS Yeast Res. 8:204-216.
• Virginia D Marks, Shannan J Ho Sui, Daniel Erasmus, George K van der Merwe, Jochen Brumm, Wyeth W Wasserman, Jenny Bryan, and Hennie J J van Vuuren. 2008. Dynamics of the Yeast Transcriptome During Wine Fermentation Reveals the Fermentation Stress Response. FEMS Yeast Res.8:35-52.
• Joana Coulon, John I Husnik, Debra L Inglis, George K van der Merwe, Aline Lonvaud, Daniel J Erasmus and Hennie J J van Vuuren. 2006. Metabolic engineering of Saccharomyces cerevisiae to minimize the production of ethyl carbamate in wine. Am. J. Enol. Vitic. 57(2):113-124.
• Subden, R.E., Husnik, J.I., van Twest, R., van der Merwe, G.K., and van Vuuren, H.J.J. 2003. Autochthonous microbial population in a Niagara Peninsula icewine must. Food. Res. Int. 36:747-751.
• Erasmus, D.J., van der Merwe, G.K., and van Vuuren, H.J.J. 2003. Genome-wide expression analyses: Metabolic adaptation of Saccharomyces cerevisiae to high sugar stress. FEMS Yeast Res. 3:375-399.
• Marks, V.D., van der Merwe, G.K., and van Vuuren, H.J.J. 2003. Transcriptional profiling of wine yeast in fermenting grape juice: Regulatory effect of di-ammonium phosphate. FEMS Yeast Res. 3:269-287.
• Dhanawansa, R., Faridmoayer, A., Li, P., van der Merwe, G.K., and Scaman, C. 2002. Overexpression, purification, and partial characterization of Saccharomyces cerevisiae processing alpha glucosidase I. Glycobiology 12:229-234.
• van der Merwe, G.K., van Vuuren, H.J.J., and Cooper, T.G. 2001. Ammonia regulates VID30 expression and Vid30p function shifts nitrogen metabolism towards glutamate formation especially when Saccharomyces cerevisiae is grown in low concentrations of ammonia. J. Biol. Chem. 276:28659-28666.
• van der Merwe, G.K., van Vuuren, H.J.J., and Cooper, T.G. 2001. Cis-acting sites contributing to expression of divergently transcribed DAL1 and DAL4 genes in Saccharomyces cerevisiae: a word of caution when correlating cis-acting sequences with genome-wide expression analyses. Curr. Genet. 39:156-165.
• Richard Preiss, Eugene Fletcher, Lars Marius Garshol, Barret Foster, Emine Ozsahin, Mark Lubberts,George van der Merwe, and Kristoffer Krogerus. (2024). European Farmhouse Brewing yeast form a distinct genetic group. Applied Microbiology and Biotechnology. DOI: 10.1007/s00253-024-13267-3
• Barret Foster, Caroline Tyrawa, Emine Ozsahin, Mark Lubberts, Kristoffer Krogerus, Richard Preiss and George van der Merwe. (2022). Kveik Brewing Yeasts Demonstrate Wide Flexibility in Beer Fermentation Temperature Tolerance and Exhibit Enhanced Trehalose Accumulation. Frontiers inMicrobiology. DOI: 10.3389/fmicb.2022.747546

Postdoctoral Fellow

• Dr. Barret Foster

ResearchTechnician

• Bryan Chalk

Graduate students

• Jordan Willis (Ph.D. candidate)
• Ebad Mazhar (MBINF)
• Tomas Fischer (MSc)

Recent alumni

• Dr. John Turner (PDF)
• Dr. Viola Halder (PDF)
• Dr. Emine Ozsahin (PDF)
• Dr. Hollie Rowlands (PDF)
• Barret Foster (Ph.D.)
• Jessica Nelson (M.Sc.)
• Jordan Hofstra (M.Sc.)
• Jesse Rentz (Research Technician)
• Caroline Tyrawa (Research Technician)

MICR*2420: Introduction to Microbiology

MCB*4500/4510: Research Project in Molecular and Cellular Biology. I participate in these courses to provide senior undergraduate students with opportunities to do research projects. For more detail about such opportunities in my lab, please contact me directly.

BIOT*6550: Biodiversity and Biotechnology