Recombinant luminescent bacteria for measuring bioavailable arsenite and antimonite

Luminescent bacterial strains for the measurement of bioavailable arsenite and antimony were constructed. The expression of firefly luciferase was controlled by the regulatory unit of the ars operon of Staphylococcus aureus plasmid pI258 in recombinant plasmid pTOO21, with S. aureus RN4220, Bacillus subtilis BR151, and Escherichia coli MC1061 as host strains. Strain RN4220(pTOO21) was found to be the most sensitive for metal detection responding to arsenite, antimonite, and cadmium, the lowest detectable concentrations being 100, 33, and 330 nM, respectively. Strains BR151(pTOO21) and MC1061(pTOO21) responded to arsenite, arsenate, antimonite, and cadmium, the lowest detectable concentrations being 3.3 and 330 microM and 330 and 330 nM with BR151(pTOO21), respectively, and 3.3, 33, 3.3, and 33 microM with MC1061(pTOO21), respectively. In the absence of the mentioned ions, the expression of luciferase was repressed and only a small amount of background light was emitted. Other ions did not notably interfere with the measurement in any of the strains tested. Freeze-drying of the cells did not decrease the sensitivity of the detection of arsenite; however, the induction coefficients were somewhat lower.