ABSTRACT
This chapter discusses the factors affecting the fitness and the survival of yeast species in nature, with little emphasis on how people may apply that knowledge in the search for useful yeast strains. Numerous surveys of substrates that were suspected to harbour yeasts, because of the availability of the necessary nutrients for their growth, have revealed that yeasts appear to be far less ubiquitous than many bacterial species. Unlike bacteria, yeasts are relatively modest in their physiological abilities. They are strictly organotrophic, which restricts the range of habitats in which yeasts may be recovered in some abundance. Yeast habitats have less of a geographic component than plant or animal habitats. The distribution of yeast species in nature is most intimately tied to the distribution of host plants, and in some cases host animals, in their own habitats. The perception of yeasts as members of communities profoundly influences the methodological approaches used to study natural yeast populations.
