Astrobiology

Origins of Life and Evolution of Biospheres

, Volume 42, Issue 2, pp 201-221

Extremophilic Acinetobacter Strains from High-Altitude Lakes in Argentinean Puna: Remarkable UV-B Resistance and Efficient DNA Damage Repair

  • Virginia Helena AlbarracínAffiliated withPlanta Piloto de Procesos Industriales y Microbiológicos (PROIMI), CCT, CONICETFacultad de Ciencias Naturales e Instituto Miguel Lillo, Universidad Nacional de TucumánMax-Planck-Institute for Bioinorganic Chemistry
  • , Gopal P. PathakAffiliated withMax-Planck-Institute for Bioinorganic Chemistry
  • , Thierry DoukiAffiliated withLaboratoire “Lésions des Acides Nucléiques” INaC/SCIB UMR-E3 CEA-UJF/CEA-Grenoble
  • , Jean CadetAffiliated withLaboratoire “Lésions des Acides Nucléiques” INaC/SCIB UMR-E3 CEA-UJF/CEA-Grenoble
  • , Claudio Darío BorsarelliAffiliated withInstituto de Química del Noroeste Argentino (INQUINOA), CONICET, Facultad de Agronomía y Agroindustrias, Universidad Nacional de Santiago del Estero
  • , Wolfgang GärtnerAffiliated withMax-Planck-Institute for Bioinorganic Chemistry Email author 
  • , María Eugenia FariasAffiliated withPlanta Piloto de Procesos Industriales y Microbiológicos (PROIMI), CCT, CONICET Email author 

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Abstract

High-Altitude Andean Lakes (HAAL) of the South American Andes are almost unexplored ecosystems of shallow lakes. The HAAL are recognized by a remarkably high UV exposure, strong changes in temperature and salinity, and a high content of toxic elements, especially arsenic. Being exposed to remarkably extreme conditions, they have been classified as model systems for the study of life on other planets. Particularly, Acinetobacter strains isolated from the HAAL were studied for their survival competence under strong UV-B irradiation. Clinical isolates, Acinetobacter baumannii and Acinetobacter johnsonii, served as reference material. Whereas the reference strains rapidly lost viability under UV-B irradiation, most HAAL-derived strains readily survived this exposure and showed less change in cell number after the treatment. Controls for DNA repair activity, comparing dark repair (DR) or photo repair (PR), gave evidence for the involvement of photolyases in the DNA repair. Comparative measurements by HPLC-mass spectrometry detected the number of photoproducts: bipyrimidine dimers under both PR and DR treatments were more efficiently repaired in the HAAL strains (up to 85 % PR and 38 % DR) than in the controls (31 % PR and zero DR ability). Analysis of cosmid-cloned total genomic DNA from the most effective DNA-photorepair strain (Ver3) yielded a gene (HQ443199) encoding a protein with clear photolyase signatures belonging to class I CPD-photolyases. Despite the relatively low sequence similarity of 41 % between the enzymes from Ver3 and from E. coli (PDB 1DNPA), a model-building approach revealed a high structural homology to the CPD-photolyase of E. coli.

Keywords

Acinetobacter Extremophiles High-Altitude Andean Lakes Photolyase UV-resistance