The overall objective of this study is to understand the geochemical controls on tetracycline speciation governing induction and expression of microbial antibiotic resistance in water. Tetracycline generally manifests several species in aqueous phase. E. coli whole-cell bioreporter was used as a tool to investigate bioavailability of tetracycline in solution under varying conditions (pH, cations and ligands). The results revealed that the activities of the bioreporter responded in a linear manner to tetracycline intracellular concentrations. At a higher pH (e.g. 8.0) tetracycline demonstrated a reduced bioavailability as compared to that in the solutions at pH of 6.0 and 7.0. Mg2+ and Ca2+ present in the solution bound to tetracycline and formed metal-tetracycline complexes, hence reducing tetracycline bioavailability. Among the species of tetracycline present in solution including tetracyclines and metal-complexed species, we identified zwitterions of tetracycline to be the primary species responsible for triggering the expression of antibiotic resistance.

Tetracycline speciation controls expression of bacterial antibiotic resistance

243rd National Meeting (2012)

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