Immobilization is considered a feasible strategy for addressing toxicity and nanomaterial pollution confronted by nano-catalysts in practical applications. A research team from ShanghaiTech University harvested genetically engineered Escherichia coli biofilms as living substrates to immobilize nanoscale catalysts. The biofilm matrix provides a benign and robust interface between nano-catalysts and living cells, upon which three tunable and recyclable catalytic reaction systems has been demonstrated.