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/cm<sup>2</sup>, 48.5 μW/cm<sup>2</sup>, and
511 W/m<sup>2</sup>, 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 5x10<sup>5</sup> 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.