Cadmium (Cd) and mercury (Hg) toxicity are reduced by probiotic Escherichia coli Nissle, citric acid, and pyrroloquinoline quinone (PQQ).
EcN-20 secretes PQQ along with external citric acid reduces Cd and Hg toxicity.
Artificial citrate operon was incorporated into EcN-20 to produce 2 mM citric acid.
Citric acid secretion by EcN-21 is insufficient to reduce Cd and Hg toxicity.