Ecological structuring of yeasts associated with trees around Hamilton, Ontario, Canada.

This study seeks to determine the distribution and diversity of yeasts in and around the Hamilton area in Canada. In light of the increasing number of fungal infections along with rising morbidity and mortality rates, especially among the immunocompromised, understanding the diversity and distribution of yeasts in natural environments close to human habitations has become an increasingly relevant topic. In this study, we analyzed 1110 samples obtained from the hollows of trees, shrubs and avian droppings at 8 geographical sites in and around Hamilton, Ontario, Canada. A total of 88 positive yeast strains were isolated and identified belonging to 20 yeast species. Despite the relative proximity of the sampling sites, our DNA fingerprinting results showed that the yeast populations were highly heterogenous. Among the 14 tree species sampled, cedar, cottonwood and basswood hollows had relatively high yeast colonization rates. Interestingly, Candida parapsilosis was isolated almost exclusively from Pine trees only. Our results are consistent with microgeographic and ecological differentiation of yeast species in and around an urban environment.