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Microbial Transformations of Arsenic in the Environment: From Soda Lakes to Aquifers

¹ School of Earth, Atmospheric and Environmental Sciences, and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester M13 9PL, UK E-mail: jon.lloyd{at}manchester.ac.uk
² United States Geological Survey, Ms 480, 345 Middlefield Rd, Menlo Park, CA 94025, USA E-mail: roremlan{at}usgs.gov

Arsenic is a highly toxic element that supports a surprising range of biogeochemical transformations. The biochemical basis of these microbial interactions is described, with an emphasis on energy-yielding redox biotransformations that cycle between the As⁵⁺ and As³⁺ oxidation states. The subsequent impact of As³⁺-oxidising and As⁵⁺-reducing prokaryotes on the chemistry of selected environments is also described, focusing on soda lakes with naturally high concentrations of the metalloid and on Southeast Asian aquifer sediments, where the microbial reduction of sorbed As⁵⁺ and subsequent mobilisation of As³⁺ into water abstracted for drinking and irrigation threaten the lives of millions.

KEYWORDS: metal reduction, metal oxidation, metal resistance, biogeochemical cycles, arsenic poisoning