Gut Escherichia coli expressing Pb2+-adsorption protein reduces lead accumulation in grass carp, Ctenopharyngodon idellus

Highlights: • A lead-specific adsorption strain E. coli PbBD was constructed. • E. coli PbBD effectively reduced Pb²⁺ accumulation and helped Pb²⁺ excretion in fish. • E. coli PbBD helped protecting intestinal health and microbial homeostasis under Pb²⁺ stress. • E. coli PbBD posed no adverse effect on fish, thus can be a useful lead-removal tool in fish. Lead (Pb²⁺) is easy to accumulate in fish which become a major source of Pb²⁺ exposure to humans. In this study, a recombinant Escherichia coli strain expressing Pb²⁺-specific surface-binding protein anchored by the ice nucleation protein was introduced into grass carp (Ctenopharyngodon idellus) gut to investigate its protective effect against dietary Pb²⁺ exposure. Pb²⁺ mostly precipitated on the surface of the engineered strain through Pb²⁺-specific surface-binding protein, with a maximum adsorption efficiency of 73% and an adsorption capacity of 163 μmol/g dry cells. The Pb²⁺ concentration in engineered bacteria-fed grass carp was reduced significantly, and the residual level of Pb²⁺ in feces was increased by 76%, compared with the control group. Meantime, the engineered bacteria were able to mitigate the oxidative stress and histological alterations of intestines and dysbiosis of gut microbiota induced by Pb²⁺exposure. Thus, the engineered bacterium that can effectively reduce Pb²⁺ residue in grass carp might be a useful tool for decontamintion of lead in aquatic organisms.