Figure 3.

A biosensor for methylated and aromatic arsenicals. An E. coli cell-based biosensor was constructed that reports the sensing of environmental arsenicals by GFP fluorescence. The components of the biosensor are the gene for the AfArsR repressor, shown as the structural model, and the gene for GFP, shown by evolving fluorescence of the bacterial sensor in the minitubes. The biosensor responds to trivalent aromatic arsenicals, such as phenylarsenite (PhAs(III)) or Rox(III), with the highest affinity, responds to the reduced form (MAs(III)) of the herbicide MSMA with intermediate affinity and shows very low response to inorganic As(III).