Fig. 1. Periplasmic biomineralization would provide biointerfaces for modulation and sustainability.

(A) An illustration of aquatic and biomineralized soft-hard composites with a wide range of length scales and a variety of structures and functions. Examples include fish scales, coccoliths, and the proposed nanostructured exoskeletons in the periplasm of Gram-negative bacteria. The scale bars are only representative. (B) Schematic illustrating the synthesis of semiconductor nanoclusters within the periplasm of Gram-negative bacteria. The periplasm is the space between the inner membrane (IM) and the outer membrane (OM). (C to E) Electron and x-ray microscopy images of the biohybrids. Pseudo-colored scanning electron microscope (SEM) image (C) showing E. coli (green) with extensive amounts of fimbriae (purple). STEM image (D) and energy dispersive x-ray spectroscopy (EDS) mapping (E) showing that bacterial cell can mineralize semiconductor clusters composed of multiple elements, including Cd, Pb, and Hg, within the periplasm in single bacterial cell. (F) We demonstrate that our biohybrid system with periplasmic biomineralization could enable metal removal, as well as semi-artificial photosynthesis, and construct a living reactor. The biomineralized semiconductor nanoclusters may couple the photoelectrons with the microbial metabolism to enhance the biosynthesis under light.