Arsenic contamination of ground water affects the health of millions of people worldwide. Bioremediation has the potential to lower contaminant levels in cases where physical methods are either ineffective or cost prohibitive. The yeast Saccharomyces cerevisiae was engineered for enhanced arsenite accumulation by overexpression of transporters responsible for the influx of the contaminant. The transporter genes FPS1 and HXT7 were cloned under the control of the late-phase ADH2-promoter. This allowed for protein production at high biomass levels without the addition of inducer. Following the transfer of stationary phase cells to buffer, the engineered strains were capable of 3-4-fold greater arsenic uptake as compared to control cells. Further, at trace levels of the metalloid, the cells overexpressing the Fps1p transporter removed ca. 40% more arsenite from the extracellular medium than the controls. Arsenic uptake was also evaluated in cells overexpressing the transporters coupled with high-level production of cytosolic As sequestors (phytochelatins or bacterial ArsRp) to act as an intracellular sink. This led to an up to 4-fold increase in As accumulation in the resting cell culture as compared to native cells. The results demonstrate important steps needed to engineer a yeast biosorbent with enhanced accumulation capabilities for this metalloid.
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