SENSING ANTIMONITE AND ARSENITE AT THE SUBATTOMOLE LEVEL WITH GENETICALLY-ENGINEERED BIOLUMINESCENT BACTERIA

A highly sensitive and selective optical sensing system for antimonite has been developed using genetically engineered bacteria. The basis o f this system is the ability of certain bacteria to survive in environ ments that are contaminated with antimonite, arsenite, and arsenate, T he survival is conferred to the bacteria by the ars operon, which cons ists of five genes that code for three structural proteins, ArsA, ArsB , and ArsC, and two regulatory proteins, ArsD and ArsR. ArsA, ArsB, an d ArsC form a protein pump system that extrudes antimonite, arsenite, and arsenate once these anions reach the cytoplasm of the bacterium. A method was developed for monitoring antimonite and arsenite by using a single plasmid that incorporates the regulatory gene of the extrusio n system, arsR, and the genes of bacterial luciferase, luxA and luxB. In the designed plasmid, ArsR regulates the expression of bacterial lu ciferase in a manner that is dependent on the concentration of antimon ite and arsenite in the sample. Thus, the bioluminescence emitted by l uciferase can be related to the concentration of antimonite and arseni te in the sample. Concentrations for antimonite and arsenite in the or der of 10(-15) M, which corresponds to subattomole levels, can be dete cted. This bacterial-based sensing system is highly selective for anti monite and arsenite.