UV radiation as an enhancer of bacterial survival in extreme environments?

MARÍA E. FARÍAS; MARÍA R. FLORES; OMAR F. ORDOÑEZ

Philadelphia

Congreso; 109th Society for General Meeting of the American Microbiology; 2009

American Society for Microbiology

Background: The Argentine Andean lakes are a system of shallow lakes distributed across the Puna (high plateau) at altitudes varying from 4,200 m to 6,000 m above sea level. These aquatic ecosystems present extreme environmental conditions mainly high levels of Ultraviolet Radiation (UV). The aim of this work is to determine the incidence of UV in microbial communities from these environments. Puna (high plateau) at altitudes varying from 4,200 m to 6,000 m above sea level. These aquatic ecosystems present extreme environmental conditions mainly high levels of Ultraviolet Radiation (UV). The aim of this work is to determine the incidence of UV in microbial communities from these environments. Puna (high plateau) at altitudes varying from 4,200 m to 6,000 m above sea level. These aquatic ecosystems present extreme environmental conditions mainly high levels of Ultraviolet Radiation (UV). The aim of this work is to determine the incidence of UV in microbial communities from these environments. Puna (high plateau) at altitudes varying from 4,200 m to 6,000 m above sea level. These aquatic ecosystems present extreme environmental conditions mainly high levels of Ultraviolet Radiation (UV). The aim of this work is to determine the incidence of UV in microbial communities from these environments. The Argentine Andean lakes are a system of shallow lakes distributed across the  Puna (high plateau) at altitudes varying from 4,200 m to 6,000 m above sea level. These aquatic ecosystems present extreme environmental conditions mainly high levels of Ultraviolet Radiation (UV). The aim of this work is to determine the incidence of UV in microbial communities from these environments. Methods: Studies were performed in samples from 4 high Andean lakes: Laguna Negra (L. Negra; 4,400 m), L. Verde (4,460 m), L. Vilama (4,600 m) and L. Chiro (4,500 m). Experiments in total communities assemblage by measuring denaturing gradient gel electrophoresis (DGGE), Fluorescent in situ Hybridization (FISH) and accumulation of Cyclobutane Pyrimidine Dimers (CPDs). In the same way isolation of bacteria under UV-B stress was done. In isolated bacteria cell count, CPD accumulation and mutagenesis incidence were measured. Results: Although CPDs accumulation increased with UV exposition, DGGE profiles of the samples from the four lakes showed no decrease in the number of bands along UV radiation exposure. In fact, the number and the intensity of many bands increased comparing dark controls. Similar results were found by FISH counts since the number of cells increased among 2 magnitude order comparing dark controls. Concerning exposed isolated it was found that bacteria belonging to Exiguobacterium sp., and Acinetobacter sp. genera increased their cell number under UV stress.  In all the cases CPD accumulation increased with UV exposition (until 640 CPD/MB) comparing dark controls. Conclusion: From the findings it can be inferred that UV radiation would have no or little effect on communities in high altitude lakes. Moreover, the noticeable increase in the number of cells and enrichment of the microbial diversity could preliminarily be explained by the fact that UV triggered certain mechanisms that enhanced the ability of cells to survive, or the fact that certain cells obtained energy from UV radiation. Our findings could be the base for further studies directed to explain the high tolerance to UV radiation in these extreme communities.