title: Biosensor for organoarsenical herbicides and growth promoters.
abstract: The toxic metalloid arsenic is widely distributed in food, water, and soil. While inorganic arsenic enters the environment primarily from geochemical sources, methylarsenicals either result from microbial biotransformation of inorganic arsenic or are introduced anthropogenically. Methylarsenicals such as monosodium methylarsonic acid (MSMA) have been extensively utilized as herbicides, and aromatic arsenicals such as roxarsone (Rox) are used as growth promoters for poultry and swine. Organoarsenicals are degraded to inorganic arsenic. The toxicological effects of arsenicals depend on their oxidation state, chemical composition, and bioavailability. Here we report that the active forms are the trivalent arsenic-containing species. We constructed a whole-cell biosensor utilizing a modified ArsR repressor that is highly selective toward trivalent methyl and aromatic arsenicals, with essentially no response to inorganic arsenic. The biosensor was adapted for in vitro detection of organoarsenicals using fluorescence anisotropy of ArsR-DNA interactions. It detects bacterial biomethylation of inorganic arsenite both in vivo and in vitro with detection limits of 10(-7) M and linearity to 10(-6) M for phenylarsenite and 5 × 10(-6) M for methylarsenite. The biosensor detects reduced forms of MSMA and roxarsone and offers a practical, low cost method for detecting activate forms and breakdown products of organoarsenical herbicides and growth promoters.
authors.affiliation: Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University , Miami, Florida 33199, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Samio
authors.initials: S
authors.lastname: Sun
authors.forename: Chen-Zhong
authors.initials: CZ
authors.lastname: Li
authors.forename: Yong-Guan
authors.initials: YG
authors.lastname: Zhu
authors.forename: Barry P
authors.initials: BP
authors.lastname: Rosen
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000032:analysis / Q000494:pharmacology; D001151:Arsenic / Q000032:analysis* / Q000494:pharmacology; D001152:Arsenicals / Q000032:analysis* / Q000494:pharmacology; D015374:Biosensing Techniques / Q000379:methods*; D001711:Biotransformation; D004926:Escherichia coli / Q000187:drug effects / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D048788:Growth and Development / Q000187:drug effects; D006540:Herbicides / Q000032:analysis*; D008745:Methylation / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D011200:Poultry / Q000378:metabolism; D012406:Roxarsone / Q000032:analysis / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; C489527:ArsR protein, E coli; D001152:Arsenicals; D029968:Escherichia coli Proteins; D006540:Herbicides; D015534:Trans-Activators; D012406:Roxarsone; C020300:monomethylarsonic acid; D001151:Arsenic