Diversity and extracellular enzymatic activity of culturable yeasts isolated from soil in a Brazilian Amazonian rainforest biome.

The Amazon rainforest represents the largest and most biodiverse tropical rainforest in the world, comprising over half of the planet's remaining rainforests. In this study, we investigated the yeast distribution in the soils in a Brazilian Amazonian rainforest biome. The collection sites included two upland forests, a black-water floodplain forest, and an Amazonian dark earth site. Yeasts were isolated using both enrichment and direct isolation techniques, with different incubation temperatures. We obtained a total of 598 yeast and yeast-like isolates belonging to 110 species. The highest yeast diversity was obtained using the enrichment isolation procedure. Species richness and Shannon diversity were higher in the upland forests than in the other sites. Lipomyces species were only recovered when a nitrogen-free medium was used. Among 314 isolates tested, 85.5% produced at least one extracellular enzyme capable of degrading proteins, esters, xylan, starch, lipids, pectin, cellulose, or tannins. About 45% of the yeasts also solubilized phosphate. Forty-five possible candidates for new species were identified, indicating that soil is a significant source of novel yeasts in Amazonian rainforest biomes.