Biodiversity and Adaptation Mechanisms of Extremophiles Thriving in the Highest UV-Exposed Ecosystems on Earth

ALBARRACÍN V. H.; FARIAS M.E.

Córdoba

Congreso; 16th International Congress on Photobiology; 2014

The High-Altitude Andean Lakes (HAAL) at the Dry Central Andes region comprise a set of pristine shallow lakes and salt flats, locally called as ?Lagunas? (L) or ?Salares? (S), distributed along a wide range of altitudes (2,000 to 6,000 m) and exposed to a unique combination of extreme conditions (high solar total and UV radiation, hypersalinity, large daily thermal amplitude, desiccation, hiperaridity). The aim of this work is to present the diversity of microbial communities thriving at the HAAL which, in accordance with their original niche characteristics, displayed high UV-resistance. Evidence regarding the diverse photoprotection and photorepairing mechanisms of these extremophiles is obtained by using a multidisciplinary approach that goes from environmental microbiology through genomics to photochemistry. An outstanding microbial biodiversity was observed in most HAAL niches: water, sediments, soil, fumaroles, evaporites, microbial mats, and even in multi-layered flat mats and stubby pillars called stromatolites (Farias et al., 2013). Due to the high altitude and the geographical and physicochemical characteristics of HAAL, UV radiation is one of the most limiting abiotic factors for HAAL microbial communities: solar irradiance is much higher than at sea level with instantaneous UV-B flux reaching 17 W m−2 in some lakes (compared with 0,1-0,4 W m−2 at the sea level). In accordance with this, almost one hundred UV-resistant strains were isolated, characterized and identified as belonging to diverse taxonomic groups (Ordoñez et al., 2009; Bequer-Urbano et al., 2013). Several mechanisms are described as the base behind this high UV-resistance profile: i) photoprotection and negative phototaxis in a stratified microbial community (Farias et al., 2013); ii) competent protection against reactive oxygen species (ROS), potentially damaging agents for lipids, proteins and nucleic acids (Di Capua et al., 2011; Bequer Urbano et al., 2013); iii) capability of bypassing DNA lesions and high mutagenic frequencies (Fernandez Zenoff et al., 2008); and iv) efficient repairing ability of DNA photoproducts (Albarracin et al., 2012; 2014). The scenario pictured herein makes the HAAL microorganisms excellent test cases for exploring novel enzymatic functions driven by light, and for the bioprospection of novel molecules with potential biotechnological applications on energy conversion, biomedicine or industry. This brief overview is intended to "shine" scientific light on a high window from a quite unexplored, exotic environment, which otherwise constitutes an exceptional outdoor photobiology lab. [1] V. H. Albarracín, G. Pathak, T. Douki, J. Cadet, C. Borsarelli, W. Gärtner, M. E. Farias, Origin of Life and Evolution of Biospheres, 2012, 42, 201-221. [2] V. H. Albarracín, J. Simon, G. Pathak, L. Valle, T. Douki, J. Cadet, C. Borsarelli, M. E. Farias, W. Gärtner, 2014, Photochem. Photobiol. Sci., DOI: 10.1039/C3PP50399B. [3] S. Bequer Urbano, V. H. Albarracín, O. Ordoñez, M. E. Farías, and H. Alvarez, Extremophiles, 2013, 17, 217-227. [4] C. Di Capua, A. Bortolotti, M. E. Farías, N. Cortez, 2011, FEMS Microbiol Lett, 317, 181?189. [5] M. E. Farias, N. Rascovan, D. M. Toneatti, V. H. Albarracin, M. R. Flores, D. G. Poire, M. M. Collavino, O.M. Aguilar, M.P. Vazquez, and L. Polerecky, 2013, PLoS One 8, e53497. [6] V. Fernandez Zenoff, F. Sineriz, M. E. Farias, 2006, Appl Environ Microbiol, 72, 7857-63. [7] O. F. Ordoñez, M. R. Flores, J. R. Dib, A. Paz, M. E. Farias, 2009, Microb Ecol, 58, 461-73.