by Teun Boekhout, Utrecht, 6 December 2017
The father of modern yeast taxonomy, Dr. Cletus Kurtzman, passed away Monday, November 27 2017, after a heart attack thus leaving the yeast biodiversity research community in shock.
Clete worked for 50 years as a yeast researcher at the U.S. Department of Agriculture-ARS laboratory in Peoria, Illinois of which 29 years as a group leader, and he was internationally very much recognized for his pioneering contributions to the molecular phylogeny and – taxonomy of yeasts, mainly belonging to Saccharomycotina.
Clete was the first who recognized the power of comparative molecular phylogenetic studies and started studying this from the 1980s. Clete already in the early days of his scientific career used DNA-based methods, such as DNA-DNA reassociation studies and estimation of Mol. % guanine and cytosine in his studies. However, after the development of PCR he started to use nucleotide sequence information, particularly of the D1/D2 domains of the large subunit of the ribosomal DNA, and implemented this information into the taxonomy of yeasts. In his work he assessed the amount of nucleotide divergence at different taxonomic levels, including the species, and he revised the taxonomy of ascomycetous yeasts with known sexual states. His contributions paved the road from many other researchers who started to implement similar approaches in different yeasts, and, later, also filamentous fungi. Although he clearly saw the importance of such molecular studies, he was also aware of the need of more classical data on mode of reproduction and nutritional physiology.
Clete also lectured and taught many courses on yeast diversity and taxonomy for young scientists from many countries, e.g. Brazil, Mexico, Portugal, and China, and served as an editor for eight scientific journals. He also (co-)edited the 4th and the 5th edition of The Yeasts, a Taxonomic Study, the widely used encyclopaedia on yeast diversity.
Working at a USDA laboratory, applied features of yeasts, including applications in biotechnology and clinical diagnostics, had his interest as well. The mental flexibility of Clete became also clear as he was still actively involved in the next technical breakthrough in yeast diversity, namely the use of whole genome data for a better understanding of yeast diversity, including functional aspects.
Until the very last moment Clete has been a very active scientist highly interested in the future of yeast taxonomy, including nomenclatural aspects, and he interacted with many scientists worldwide. He (co-)authored more than 350 scholarly publications that resulted in > 23,000 citations and is present in the ARS Science Hall of Fame since 2016. Clete was a fellow of the American Academy of Microbiology and in 2008 he was the first awardee of the Josef Adolf von Arx award given by the Westerdijk Fungal Biodiversity Institute in Utrecht, The Netherlands. He also served as the USA representative in the International Commission of Yeasts of the International Union of Microbiological Societies. In a recent interview he replied ‘Because I am still quite excited about my work with the yeasts, it is hard to think that I might do something else.’ Clearly indicating his passion for the microbes he studied lifelong.
On a personal note it has been a great pleasure to work as a postdoc in his laboratory in 1992, to enjoy his somewhat dry sense of humour when we met at meetings having a beer [or two], and he has always been a family man, showing keen interest in the well-beings of (my) family members. He was very much worried about his wife Mary Ann as her health deteriorated during the last years, and he was a proud father of his children and a great grandfather to his five grandchildren. He will be missed by them and by us from the yeast research field. Clete has been an editor for FEMSYR from the beginning. As a token of appreciation the journal will publish an extensive overview of Clete’s scientific achievements in 2018, as well a number of reviews on the impact his work had on various areas of yeast research.