Bacterial diversity associated to arsenic contamination in Salar de Ascotán, Chile

LARA J.A; DEMERGASSO C.; FERRERO M.A

Rosario, Argentina

Congreso; V Congreso Argentino de Microbiología General; 2008

(SAMIGE) SOCIEDAD ARGENTINA DE MICROBIOLOGIA GENERAL

AMB 10 Bacterial diversity associated to arsenic contamination in Salar de Ascotán, Chile [Quiere dar POSTER] [Modificar] [Borrar] José A. Lara1, Cecilia Demergasso2, Marcela A. Ferrero1 1 PROIMI-CONICET 2 Centro de Biotecnologia, Universidad Catolica de Norte, Antofagasta, CHILE () Andean Puna is a special place with unique geological, geomorphologic and climate characteristics. These characteristics promoted the formation of extensive salt flats in the Andes in conjunction with geothermal processes and evaporation of water rich in arsenic and other compounds (borates, nitrates, etc.). Microbial diversity inhabiting these environments is poorly studied, however, these ecosystem provide a unique collection of habitats for studying microbial diversity in relation to salinity and arsenic deposits. Bacteria have been identified that can oxidize and/or reduce arsenic compounds for energy conservation in many environments. Activities of mobilizing and precipitation of arsenic were demonstrated in contaminated sediments of River Loa and Salar de Atacama, in northern Chile. We analyzed the planktonic bacterial assemblages inhabiting Salar de Ascotán, a salt flat of the II Region of Chile, by PCR- denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rRNA gene fragments. Laguna Turquesa samples was specially analyzed because their high concentration of total arsenic (28 mg ml-1). Culturable, arsenic-precipitating cells were detected by most-probable-number (MPN) incubations. The presence of yellow precipitate was considered as a positive result. DGGE approach was used to characterized bacterial population in sediment samples, as well as those obtained by enrichment cultures at different temperatures (4 and 30 ºC), and concentrations of As(III) and As(V), incubated in aerobic and anaerobic conditions. From a total of nearly one hundred of bands obtained in DGGE profiles, only 40 % could be reamplified and sequenced, obtaining sequences with identities between 94 and 99 % with those deposited in database. From these, nearly to 70 % belong to uncultured bacteria (DGGE bands or clones). Bacillus, Alkaliphilus and Paraliobacillus were found as bacterial isolates and cited by other authors as halotolerant or halophile, metabolically related to metallic compounds reductions and isolated from extreme environments.Respect to the incubation temperature, with exception of only one sequence (unc. marine bacterium clone A3, identity 98 %) found at 4 and 30 ºC, the rest of the sequences grouped in one or other temperature condition. Conglomerate analysis in order to compare DGGE profiles at different enrichment conditions, allow finding a major grouping of similar profiles by temperature, clearly observing 4 groups or nods that differed at more than 50% of maximum distance.