The intimate relationship between man and yeast : it's complicated
Inaugural address delivered on 6 June 2011 by prof Alf Botha.Yeasts public health service; resource allocation; have been associated with mankind’s welfare for a long time. For millennia these unicellular fungi were cultivated by man as a source of food and drink. However, it was only some 140 years ago that Pasteur demonstrated that live yeast is essential for beer and wine fermentations (Pasteur, 1866; 1876). Since then, these organisms were also found to have biotechnological potential in the production of vitamins (Roman, 1957), fine chemicals (Botes et al., 2005; Miao et al., 2011), enzymes (Steyn & Pretorius, 1990), biofuel (Lynd et al., 2002) and even single-cell proteins (Du Preez, 1990; Roman, 1957). However, yeasts are not only important for industrial biotechnology, but these fungi also have potential uses in agriculture. Some yeasts were found to be beneficial for mycorrhizal interactions during which crop performance is enhanced (Fracchia et al., 2003), others inhibit growth of post harvest pathogens on damaged fruit (Chand-Goyal & Spotts, 1997; Roberts, 1990), while a few species are currently being included in biological fertilisers that are claimed to enhance soil quality. However, yeasts may also be detrimental to mankind since a number of species may act as opportunistic pathogens of humans (Ikeda et al., 2002; Lamagni et al., 2001). This phenomenon is of great importance to an ever-increasing immunocompromised human population suffering from HIV/Aids. The extraordinary progress made in yeast biology may largely be ascribed to decades of studying the intrinsic characteristics of these organisms while growing in pure culture (Kurtzman & Fell, 1998; Lodder, 1971). Thus, during the last two hundred years yeast morphology, metabolism, as well as classical and molecular biology, was always at the frontiers of the biological sciences of the time. This review takes a closer look at the reasons for man’s fascination with this versatile group of organisms and focuses on one of the new frontiers in yeast biology, that of its ecology in natural environments. However, before we can explore this realm of science, we first need to obtain a better understanding of the general characteristics of these microscopic eukaryotes that have captured the imagination of so many biologists over the decades.