Fig. 8

Schematic diagram illustrating the uptake pathway of exogenous hemin and cellular function and the access to cytochrome protein assemble in S. oneidensis MR-1 strain. Only the supplement of exogenous hemin made it possible to delete both hemH1 and hemH2 genes simultaneously in MR-1. The MR-1 strain could uptake exogenous hemin to compensate for loss of endogenous heme synthesis via the hemin uptake system. The hemin was transported into the cells and was mainly utilized to synthesize the respiration-related hemoproteins, especially the aerobic respiration-related proteins cytochrome c oxidase prior to other heme-requiring proteins such as catalase, peroxidase, and nitrate reductase. The upward red arrow indicates the upregulation of gene expression, the downward red arrow indicates the decrease of enzyme activity