Engineered Cyanobacteria-Based Living Materials for Bioremediation of Heavy Metals Both In Vitro and In Vivo.

The pollution caused by heavy metals (HMs) represents a global concern due to their serious environmental threat. Photosynthetic cyanobacteria have a natural niche and the ability to remediate HMs such as cadmium. However, their practical application is hindered by a low tolerance to HMs and issues related to recycling. In response to these challenges, this study focuses on the development and evaluation of engineered cyanobacteria-based living materials for HMs bioremediation. Genes encoding phytochelatins ( P CSs) and metallothioneins ( M Ts) were introduced into the model cyanobacterium Synechocystis sp. PCC 6803 , creating PM/6803. The strain exhibited improved tolerance to multiple HMs and effectively removed a combination of Cd ²⁺ , Zn ²⁺ , and Cu ²⁺ . Using Cd ²⁺ as a representative, PM/6803 achieved a bioremediation rate of approximately 21 μg of Cd ²⁺ /OD ₇₅₀ under the given test conditions. To facilitate its controllable application, PM/6803 was encapsulated using sodium alginate-based hydrogels (PM/6803@SA) to create "living materials" with different shapes. This system was feasible, biocompatible, and effective for removing Cd ²⁺ under simulated conditions of zebrafish and mice models. Briefly, in vitro application of PM/6803@SA efficiently rescued zebrafish from polluted water containing Cd ²⁺ , while in vivo use of PM/6803@SA significantly decreased the Cd ²⁺ content in mice bodies and restored their active behavior. The study offers feasible strategies for HMs bioremediation using the interesting biomaterials of engineered cyanobacteria both in vitro and in vivo.