Response of Extremophilic Bacteria from High Altitude Andean Lakes to UV-B Radiation Exposure

PORTERO, L.R.; ORDOÑEZ O.F.; ZANNIER, F.; FARIAS M.E.; ALBARRACÍN V. H.

Córdoba

Congreso; 16th INTERNATIONAL CONGRESS ON PHOTOBIOLOGY; 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 (UV-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 UV-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 UV-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 UV-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?. REFERENCES [1] VH. Albarracín, G. Pathak, T. Douki, J. Cadet, C. Borsarelli, W. Gärtner, ME. Farias, Extremophilic Acinetobacter Strains from High-Altitude Lakes in Argentinean Puna: Remarkable UV-B resistance and efficient DNA damage repair Origin of Life and Evolution of Biospheres, 2012, 42, 201-221. [2] VH. Albarracín, J. R. Dib, O. F. Ordoñez and M. E. Farias, A Harsh Life to Indigenous Proteobacteria at the Andean Mountains: Microbial Diversity and Resistance Mechanisms Towards Extreme Conditions, in Proteobacteria: Phylogeny, Metabolic Diversity and Ecological Effects, ed. [3] MR. Flores, OF. Ordoñez, ME. Farías (2009) Isolation of UV-B resistant bacteria from two high altitude Andean lakes (4,400 m) with saline and non saline conditions. J Gen Appl Microbiol 55: 447-458. [4]ME. Farias, N. Rascovan, DM. Toneatti, VH. Albarracin, MR. Flores, DG. Poire, MM. Collavino, OM. Aguilar, M. P. Vazquez and L. Polerecky, The discovery of stromatolites developing at 3,570 m above sea level in a High-Altitude volcanic Lake Socompa, Argentinean Andes, PLoS One, 2013, 8. [5] OF Ordoñez 1, MR Flores , JR Dib , A Paz , ME Farías . Extremophile culture collection from Andean lakes: extreme pristine environments that host a wide diversity of microorganisms with tolerance to UV radiation. Microb Ecol. 2009 Oct;58(3):461 [6] OF Ordoñez 1, E Lanzarotti , D Kurth , MF Gorriti , S Revale , N Cortez , MP Vazquez , ME Farías , AG Turjanski. Genome Sequence of the Polyextremophilic Exiguobacterium sp. Strain S17, Isolated from Hyperarsenic Lakes in the Argentinian Puna. Genome Announc. 2013 Jul 25 [6] VH. Albarracín, GP. Pathak, T. Douki, J. Cadet, CD. Borsarelli, W. Gärtner and M. E. Farias, Extremophilic Acinetobacter Strains from High-Alt