X‐Ray Fluorescence‐Assisted Bioassays to Determine the Bioremediation Capacity of a Cultured Consortium of Extremophile Microorganisms

Abstract

Contamination of water with heavy metals causes serious health problems worldwide. Bioremediation outperforms other methods in terms of cost and sustainability. In the hydrothermal system of the Domuyo volcano, in Northern Argentine Patagonia, a community of thermophilic microorganisms, dominated by filamentous cyanobacteria, grows, forming colored mats attached to rocks splashed with thermal water. Synchrotron XRF and XANES analysis of brown mats growing in a stream at 45°C and 540 μg/L of arsenic content showed both bioaccumulation and metabolization of arsenic. In this work, microbial mats growing in water at 70°C and arsenic content ranging from 600 to 900 μg/L were studied. The mats from Aguas Calientes hot spring exhibit green, salmon, and white colored layers, while those from Los Tachos geyser are white or green. EDXRF analysis showed annual variations in their elemental composition, and green mats presented the highest arsenic accumulation. The mats from Aguas Calientes were cultured in the laboratory to evaluate their in vitro remediation capacity. Elements such as phosphorous, calcium, manganese, and zinc increase their content from the culture medium. Meanwhile, arsenic and manganese concentrations increased five and two times, respectively, when the mats were cultivated for 7 days with the addition of arsenic or manganese to the culture media. This was accompanied by a 96% decrease of arsenic and manganese concentration in the medium. Based on these observations, we conclude that the thermophilic community of Domuyo can adapt to in vitro growth conditions as a sustainable source of bioremediation microorganisms.