Yeast communities associated with the bulk-soil, rhizosphere and ectomycorrhizosphere of a Nothofagus pumilio forest in northwestern Patagonia, Argentina.

Soil microorganisms play an important role in soil quality and they interact closely with vegetation. Little is known about yeast diversity and function in forest soil ecosystems and their interactions with other biotic soil components, particularly in the mycorrhizosphere. We studied the diversity of yeasts inhabiting the bulk-soil, rhizosphere and ectomycorrhizosphere of a Nothofagus pumilio forest in Nahuel Huapi National Park (Bariloche, Argentina). Ectomycorrhizal infection was observed in all N. pumilio trees studied. A total of 126 yeast isolates were obtained, including 18 known and three possibly new species. Basidiomycetous yeasts were predominant in all soil fractions, and the most frequently isolated species was Cryptococcus podzolicus. Diversity indices and multivariate analyses were used to study and compare yeast communities in the bulk-soil, rhizosphere and ectomycorrhizosphere. Yeasts able to ferment glucose were found associated with the rhizosphere. Many of the recovered yeast species were associated with lignocelluloses compound degradation, which suggest that yeast plays an important role as a decomposer in these forest soils. Each soil fraction has a distinct yeast assemblage related to their physiologic capacities and soil nutrient availability.