Engineered Microbial Platform Confers Resistance against Heavy Metals via Phosphomelanin Biosynthesis

Abstract Environmental concerns are increasingly fueling interest in engineered living materials derived from microbial sources. Melanin biosynthesis in microbes, particularly facilitated by recombinant tyrosinase expression, offers sustainable protection for the habitat of microorganisms against severe environmental stressors. However, there exists a vast urgency to optimize these engineered microbial platforms, which will amplify their protective capabilities, integrate multifaceted functions, and thereby expand their utility and effectiveness. In our work, we have genetically engineered microbial platforms capable of endogenously biosynthesizing phosphomelanin, a unique phosphorus-bearing melanin featured by its distinctive phosphate and phosphonate groups. The ability to heterogeneously biosynthesize phosphomelanin endows the microbes with enhanced resistance to heavy metals, thus safeguarding their survival in adverse conditions. Furthermore, we have upgraded these engineered microbes by integrating PET-degrading enzymes, thereby achieving effective integrated management of metallized plastic waste. This engineered microbial platform, with its phosphomelanin biosynthetic capabilities, presents significant opportunities for microbes to engage in bioengineering manufacturing, potentially serving as the next-generation guardians against global ecological challenges.