Physiological, genomic and proteomic evidences support the high UV resistance profile of Acinetobacter sp. Ver3 isolated from High Altitude Andean Lakes

DANIEL G. KURTH; ALBARRACIN VIRGINIA H.; CAROLINA BELFIORE; GORRITI MARTA F.; FARIAS MARIA EUGENIA

San Carlos de Bariloche

Congreso; V Congreso Argentino de Bioinformática y Biología Computacional; 2014

AB2C2 y el Instituto de Energía y Desarrollo Sustentable (IEDS), Centro Atómico Bariloche (CNEA)

High-Altitude Andean Lakes (HAAL) are a group of disperse shallow lakes and salterns, located at the Dry Central Andes region in South America at altitudes above 3,000 m, and exposed to a unique combination of severe conditions: i.e. high solar global and UV irradiation, hypersalinity, wide fluctuations in daily temperatures, desiccation, high pH, high concentrations of toxic elements including arsenic [1]. As it is considered one of the highest UV-exposed environments on Earth, HAAL microbes can be taken as model systems to study UV-resistance mechanisms in environmental bacteria at various complexity levels. Acinetobacter sp. Ver3, a gammaproteobacteria isolated from Laguna Verde (4,400 m) was recently proposed as a model UV-resistant microbe with highly efficient DNA damage photorepairing ability [2], as well as an efficient catalase machinery [3]. Here we present the genome sequence analyses of this extremophile together with further experimental evidence supporting the idea that this bacterium is able to cope with increased damage in DNA compared to sensitive strains. The genome analyses provided insight in the taxonomic classification of this organism, suggesting that it would be a new species, and allowed to identify resistance genes related to the harsh environment. Moreover, an ?UV-resistome? was defined, encompassing genes related to UV-damage repair on DNA (such as nucleases and glycosylases from excision repair systems), and genes conferring an enhanced capacity for scavenging the reactive molecular species responsible for oxidative damage (catalases, peroxidases and SODs). In addition, the UV response was also studied at the proteomic level, which confirmed the involvement of a specific cytoplasmic catalase, a putative regulator, and proteins associated to aminoacid and protein synthesis, among others. However, only a small number of proteins were overexpressed under UV stress, suggesting that the resistance of this bacterium might be due to efficient constitutively expressed systems.References1. Farias ME, Poiré DG, Arrouy MJ, Albarracín VH: Modern stromatolite ecosystems at alkaline and hypersaline high-altitude lakes in the Argentinean Puna. In STROMATOLITES Interact Microbes with Sediments. Volume 18. Edited by Tewari V, Seckbach J. Dordrecht: Springer Netherlands; 2011:427?441. [Cellular Origin, Life in Extreme Habitats and Astrobiology]2. Albarracín VH, Pathak GP, Douki T, Cadet J, Borsarelli CD, Gärtner W, Farias ME: Extremophilic Acinetobacter strains from high-altitude lakes in Argentinean Puna: remarkable UV-B resistance and efficient DNA damage repair. Orig Life Evol Biosph 2012, 42:201?21.3. Di Capua C, Bortolotti A, Farías ME, Cortez N: UV-resistant Acinetobacter sp. isolates from Andean wetlands display high catalase activity. FEMS Microbiol Lett 2011, 317:181?9.