Isothermal calorimetry investigations of microbial growth in As contaminated media

Arsenic is a ubiquitous contaminant related to natural weathering and industrial or agricultural activities and strongly affect the quality of cultivable soils used for the production of edible crops. Arsenic toxicity and mobility depends on chemical speciation and the oxidation state. For instance inorganic arsenite [As(III)] is more toxic and mobile than arsenate [As(V)]. Microorganisms can directly affect the redox balance As(V)/As(III) shifting it toward the species that can be easier processed and/or absorbed by scavenger plants. Isothermal calorimetry represents a powerful method to monitor directly the biological activity of such living systems since provide direct quantitative information both on the energetic and kinetic behavior. In this study, isothermal calorimetry was applied to assess the effects of As on the growth, metabolism and the As(V)/As(III) redox capability of Achromobacter sp.As5-13 strain, a well characterized microorganism isolated from an agricultural soil. Complementary classical microbiological methods were also performed in parallel.