DESIGN AND CONSTRUCTION OF GOLD-SELECTIVE BACTERIAL BIOSENSORS

CERMINATI, SEBASTIÁN; SONCINI, FERNANDO C.; CHECA, SUSANA K.

San Miguel de Tucumán

Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL "SAMIGE DEL BICENTENARIO"; 2011

Genetically engineered microorganisms have been widely used as an alternative to conventional analytical methods for detection of toxic compounds in environmental samples. In recent years, several reporter bacteria have been developed for detection of several heavy metals and metalloids, including Hg, Cr, As, Cd, Pb, Ni, Co, Zn and Cu. Gold is continuously demanded both as a valuable commodity and by modern industry because of its unique physicochemical properties that make it appropriate for many applications. Salmonella Typhimurium harbours a Au-resistance system whose expression is controlled by GolS, a transcriptional regulator of the MerR family that selectively detects Au with high sensitivity. Based on GolS, we developed whole-cell bacterial sensors that selectively detect Au using either Salmonella or a genetically engineered Escherichia coli strain as the reporter´s hosts. In the bacterial sensors, expression of the gfp reporter gene is strictly regulated by the GolS-dependent golB promoter. Due to the intrinsic characteristics of the regulatory protein, the non-pathogenic transgenic E. coli sensor exhibits low background fluorescence, high signal-to-noise ratio, and improved sensitivity for detecting Au ions in a wide range of concentrations (from 5 to 470 nM) with an estimated detection limit of ~33 nM, equivalent to ~ 6 µg l-1 (or parts per billion) Au(I). The fluorescent Au-sensing bacteria exhibited also minimal interference by chemically related metals such as Cu or Ag that are commonly found in Au deposits. These highly specific and sensitive Au detectors will allow the development of rapid and robust screening tools to improve discovery and extraction procedures.