Investigating microbial diversity and UV radiation impact at the high-altitude lake Aguas Calientes, Chile

Abstract

The High-Lakes Project is funded by the NAI and explores the highest perennial volcanic lakes on Earth in the Bolivian and Chilean Andes, including several lakes ∼6,000 m elevation. These lakes represent an opportunity to study the evolution of microbial organisms in relatively shallow waters not providing substantial protection against UV radiation. Aguas Calientes (5,870 m) was investigated (November 2006) and samples of water and sediment collected at 1, 3, 5, and 10 cm depth. An Eldonet UV dosimeter positioned on the shore records UV radiation and temperature, and is logging data year round. A UV SolarLight sensor allowed acquisition of point measurements in all channels at the time of the sampling. UVA, UVB, and PAR peaks between 11:00 am and 1:00 pm reached 7.7 mW/cm2, 48.5 μW/cm2, and 511 W/m 2, respectively. The chemical composition of the water sample was analyzed. DNA was extracted and DGGE analyses with bacterial and archaeal 16S fragments were performed to describe microbial diversity. Antibiotic resistances were established previously in similar environments in Argentine Andean wetlands. In order to determine these resistances in our samples, they were inoculated onto LB and R2A media and onto R2A medium containing either chloramphenicol, ampicillin or tetracycline. Bacterial was higher than archeal cell number determined by RT-PCR in all the samples, reaching maximum total values of 5×105 cell mL-1. DGGE results from these samples and Licancabur summit lake (5,916 m) samples were also compared. Eight antibiotic-resistant Gram negative strains have been isolated with distinct resistance patterns.