Use of a luminescent bacterial biosensor for biomonitoring and characterization of arsenic toxicity of chromated copper arsenate (CCA)

Abstract

An arsenic oxyanion-inducible Escherichia colichromosomal operon (arsRBC) has been previouslyidentified. Construction of a luciferasetranscriptional gene fusion (arsB::luxAB) showedthat ars operon expression, plus concomitantcell luminescence, was inducible in a concentration-dependent manner by arsenic salts. The present studywas conducted to evaluate the potential of the arsB::luxAB transcriptional gene fusion for use as abiosensor in monitoring the toxicity of arseniccompounds. Cultures from this gene fusion strain wereexposed to increasing concentrations of the woodpreservative chromated copper arsenate (CCA), as wellas its constituents, sodium arsenate and chromatedcopper solution (CC). Analysis of luciferase activityrevealed that the arsB::luxAB gene fusion wasexpressed in response to CCA and sodium arsenate, butnot to the CC solution. The detection limit of arsenicwas found to be 0.01 µg As/ml (10 parts perbillion, 10 ppb) and therefore well within the rangeof environmental concerns. A greater induction ofluminescence by arsenate was observed when cells werelimited for phosphate, as phosphate can act as acompetitive inhibitor of arsenate ions. Our resultssuggest that the E. coli arsB::luxAB fusionstrain has a promising future as a specific andsensitive biosensor for monitoring bioavailable levelsand toxicity of arsenic near sites where CCA-treatedwood has been used.