ABSTRACT
Antofagasta Region of Chile is worldwide recognized as severely arsenic (As) contaminated area. Due to its abundance, mainly as As (V) and As (III), certain microorganisms such as several types of bacteria have evolved. The aim of this work was to study the most relevant As resistant bacteria that exist in highly As contaminated sediments in El Tatio geyser field. Inductively coupled plasma mass spectrometry (ICP-MS) was employed to determine the concentration of As. Results showed a great accumulation of this element. The separation of bacterial cells into cytoplasmic and membrane fractions were carried out by differential centrifugation. The results demonstrated that, between 20-70% of arsenate was reduced to arsenite. Only in one case it was observed the presence of methylated species of As such as DMA and MMA.
