Arsenate uptake, concentration-dependent

Figure 7.10. Concentration-dependent kinetics of arsenate uptake in rice (Oryza sativa) roots with (closed symbols) and without iron plaque (open symbols). The curves are fitted to Michaelis-Menten kinetics, with a poor fit with iron plaque. (Adapted from Chen et al., 2005.)...

Silver et al. (18) found that resistance to arsenate in both E. coli and S. aureus was due to lowered uptake of arsenate by resistant cells. As expected, high phosphate concentrations protected cells from arsenate toxicity. Studies of resistant E. coli and S. aureus showed that the reduced arsenate uptake is due to an accelerated efflux of the toxic ions in a energy-dependent process (19,20). It was initially thought that arsenate was the extruded oxyanion, but later studies showed that arsenate had to be reduced to arsenite prior to extrusion (21,22). Rosen and Borbolla (23) showed that it was actually arsenite efflux in E. coli fhaf was ATP-dependent. 

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