High solar exposure of microbial communities at the Andes force evolution of efficient light-driven enzymatic mechanisms

Abstract

The High-Altitude Andean Lakes (HAAL)at the Dry Central Andes region comprise aset of pristine shallow lakes and salt flats,locally called as «Lagunas» (L) or «Salares»(S), distributed along a wide range of altitudes(2000 to 6000 m) and exposed to aunique combination of extreme conditions(high solar total and UV radiation, hypersalinity,large daily thermal amplitude, desiccation,hiperaridity). The aim of this work isto present how microbial communities thrivingat the HAAL have evolved different andefficient molecular mechanisms to make useand protect themselves for such high irradiation.Due to the high altitude and the geographicaland physicochemical characteristicsof HAAL, UV radiation is one of the mostlimiting abiotic factors for HAAL microbialcommunities: solar irradiance is much higherthan at sea level with instantaneous UV-Bflux reaching 17 W m»2 in some lakes (comparedwith 0,1 - 0,4 W m»2 at the sea level).In accordance with this, almost one hundredUV-resistant strains were isolated, characterizedand identified as belonging to diversetaxonomic groups. Several mechanisms haveevolved under the pressure of high solar irradiation:i) photoprotection and negative phototaxisin cooperative, stratified microbialcommunities; ii) competent protectionagainst reactive oxygen species (ROS), potentiallydamaging agents for lipids, proteinsand nucleic; iii) capability of bypassing DNAlesions and high mutagenic frequencies; iv)efficient repairing ability of DNA photoproductsand v) efficient light-driven pumps tomaximize energy inputs from the environment.The scenario pictured herein, makesthe HAAL microorganisms excellent test casesfor exploring novel enzymatic functions drivenby light, and for the bioprospection ofnovel molecules with potential biotechnologicalapplications on energy conversion, biomedicineor industry.