PROIMI   05436
PLANTA PILOTO DE PROCESOS INDUSTRIALES MICROBIOLOGICOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Archaea in microbial ecosystems associated to minerals in High Andean Wetlands: A source of biodiversity and alternative geochemical cycles
Autor/es:
FARIAS MARIA EUGENIA
Lugar:
Pto Varas
Reunión:
Congreso; XLIX Annual Meeting of Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB), the XXXVI Annual Meeting of Sociedad de Bioquímica y Biología Molecular de Chile (SBBM), the 4th Meeting of the Latin-American Protein Society and the LVI A; 2013
Institución organizadora:
SAIB PABMB
Resumen:
Andean Wetlands are extreme environments where microbial diversity develops associated to minerals, either precipitating (carbonates), or sheltering in them (gypsum). These microbes associated to minerals systems (MAM) include biofilms, microbial mats, microbialites and endoevaporites ecosystems. Herein we present the first report of a wide diversity of MAM ecosystems found in Salar de Atacama wetlands. They include mats and endo-evaporites systems associated to gypsum in Tebenquiche and mats, carbonates microbialites and ¨phytomicrobialites¨ in La Brava. All of them are high productive systems developing under multi-extreme conditions. Oxygen and Sulfide profiles demonstrated a wide diversity of metabolism that excludes oxygenic photosynthesis as the main carbon fixation system in some of these MAM. Microbial diversity also demonstrated to be very different to previous studied MAM ecosystems all over the world. In that way, Atacama´s MAM were dominated by Archaea, Planctomycetes and OP1 group. Cyanobacteria and Proteobacterias are almost absent; therefore, traditional carbon fixation through oxygenic and anoxygenic photosynthesis would be precluded. The arising question is how do these systems fix carbon? How do they obtain energy? The answer could be in the relationship among arsenic and bacteria. In that way Arsenite [As(III)] has been proposed as an ancient source of energy used by the last universal common ancestor (LUCA) based on arsenite oxidase phylogenetic analysis. However, a limited number of Archaea sequences were used to arrive to this conclusion with no experimental support for activity. In the multi-extreme Diamante Lake at Volcano Galan placed at 4650 m altitude, under extreme conditions such as high arsenic concentration, high pH, alkalinity, salinity and UV radiation and low oxygen, samples of a red biofilm in the bottom of microbialites were found. They demonstrated to be composed mainly by Haloarchaea (93%) (16S rRNA shotgun sequencing). Metagenomic analysis indicated a high abundance of arsenite oxidases (Aio) and respiratory arsenate [As(V)] reductases (ArrA) coded by Haloarchaea. Phylogenetic analysis revealed a new clade of Aio enzymes in this group of Archaea that gives stronger support to the pre-LUCA hypothesis. A pure culture of an Halorubrum strain obtained from this biofilm, showed the presence of Aio and ArrA genes, in addition a better growth in presence of As(III) than in no-arsenic control under light and mostly under dark conditions with an effective As(III) to As(V) transformation, indicating that Aio enzymes are functional. Our results demonstrate for first time, that Archaea, in particular, the Haloarchaea, can benefit from arsenic through As(III) oxidation and give a strong support to the use of As(III) as a primary source of energy in early forms of life. Therefore, MAM ecosystems in Andean wetlands would be a reservoir of extreme diversity resembling the beginning of the life on earth. Thus comprehensive study of these ecosystems, their valuation and its preservation is a challenge we face not only as scientists but also as a society ... ¨