YEAST DIVERSITY IN A MESOTROPHIC LAKE ON THE KARSTIC PLATEAU OF LAGOA-SANTA, MG-BRAZIL

The yeast diversity in a paleo-karstic lake of the Lagoa Santa plateau was studied during March 1986-March 1987. Water samples were collecte d monthly at five stations and the yeasts were isolated at 25 degrees C on Sabourad dextrose agar supplemented with 0.5% of yeast extract an d 10 mg% of chloramphenicol. August and February showed the highest nu mbers of isolates, coinciding, respectively with the beginning and the ending of stratification. Of 56 isolated species, Aureobasidium pullu lans, Candida famata, Cryptococcus albidus, Cryptococcus laurentii, Rh odotorula glutinis, Rhodotorula rubra and Trichosporon cutaneum occurr ed at the highest frequencies. A. pullulans showed greatest prevalence during the dry period (winter), whereas C. famata, Cr albidus, Cr lau rentii and Rh. rubra were prevalent during the rainy season (summer). Tr. cutaneum was distributed between July and November. Most isolates yeasts are associated with plants and soils, and are important in deco mposition of aquatic macrophytes. Furthermore, a possible role of thes e species as indicators of pollution is discussed.