Biodiversity and ecology of yeasts from patagonian high altitude lakes

LIBKIND, D., SAMPAIO, JP, VAN BROOCK, MR(GIRAUDO MARÍA ROSA)

Faro, Portugal

Simposio; 10th Symposium in Aquatic Microbial Ecology; 2007

Yeast occurrence at 5 Andean lakes located above 1400 m.a.s.l. was surveyed and the ability of the isolates to produce photo-protective compounds (PPC) like carotenoid pigments (antioxidants) and mycosporines (UV-absorbing compounds) was assessed. These aquatic environments are exposed to increased levels of UV radiation (UVR) due to high elevation, transparency and shallowness of their waters and their physical and chemical attributes were recorded. Over 90 yeast strains identified employing conventional and molecular techniques (MSP-PCR fingerprinting and rDNA sequencing) were assigned to 27 species, being Rhodotorula mucilaginosa the species most frequently isolated. Five new species of the genera Rhodotorula, Dioszegia and Cryptococcus were isolated. Total yeast cell counts ranged from 49 ± 12 to 890 ± 62 viable cells/L. Pigmented yeasts outnumbered (80-90%) their non-pigmented counterparts in lakes with extremely transparent waters (with the lowest conductivity and chlorophyll a). Moreover, in these lakes, a higher proportion (75-100%) of non pigmented species able to synthesize UV-absorbing compounds (mycosporines), was detected. Finally, UV resistance of wild strains of Rh. mucilaginosa was significantly higher than that of the type strain and that of the least transparent lake. A high biodiversity, including rare and non-described yeast species, is present in Patagonian mountain lakes and the occurrence of PPC producing yeasts seems to be related with abiotic factors like water transparency and UVR exposure. Our results indicate that UVR is an important environmental factor affecting yeast’s community structure in aquatic habitats.