RESPONSE OF EXTREMOPHILIC BACTERIA FROM HIGH ALTITUDE ANDEAN LAKES TO UV-B RADIATION EXPOSURE

LUCIANO RAÚL PORTERO; OMAR FEDERICO ORDOÑEZ; FEDERICO ZANNIER; VIRGINIA HELENA ALBARRACIN

Congreso; XVI Congreso Internacional de Fotobiología; 2014

High-Altitude Andean Lakes (HAAL) at the South American Andes are almost unexplored ecosystems of shallow lakes and salterns. HAAL are recognized by a remarkably high UV exposure, strong changes in temperature and salinity, and a high content of toxic elements, so they have been classified as model systems for the study of life on other planets. Accordingly, a wide variety of microorganisms named ?extremophiles? are able to inhabit these extreme environment due to their great capability of tolerating physical and chemical stress, mainly ultraviolet B radiation (V-B) [1-2-3]. The aim of this work was to investigate the response of three HAAL extremophilic strains to UV-B radiation: the Gram-negative Gamaproteobacterium Acinetobacter sp. Ver3 [1] and the Gram-positive Exiguobacterium sp. N39 and S17 [4-5]. A comparison of their resistance profiles with those of taxonomically-related collection strains (Acinetobacter johnsonii DSM 6963 and Exiguobacterium arantiacum DSM 6208) and E. coli KY1056 (as external controls) was also presented.The selected strains were exposed to different doses of V-B and their resistance profiles compared. Recovery after the exposure was evaluted by incubating cells under dark (DR) or light (PR) treatments. UV-B resistance was determined by measuring survival by colony forming unit counting (CFU) [5].HAAL bacteria displayed a higher resistance to V-B compared with control strains, withstanding up to 1 h and 2 h of exposition in Acinetobacter sp. and Exiguobacterium sp. respectively. In contrast, DSM 6963 and 6208 survivals were already compromised after 30 min, while E. coli KY1056 was inhibited after 15 min. In all cases, the recovery was more efficient after PR. Thus, we have quantitatively determined the V-B resistance patterns of three novel strains isolated from the HAAL which will constitute the basis for mining of their genomes made recently available in the search for genes and mechanisms supporting HAAL ?UV-resistome?