Turn on the Mtr pathway genes under pLacI promoter in Shewanella oneidensis MR-1

Background Shewanella genus is famous for applications like electron transfer in microbe fuel cells and bioremediation of heavy metals through the Mtr pathway. A potential way to enhance the electron genesis ability of Shewanella is to express exogenous mtr genes via recombinant DNA technology. Thus, to design and develop expression vectors capable of replicating in Shewanella and enhance the genetic toolbox of the same is important. Result In this study, a plasmid construct with a replication origin, rep B, and pLacI promoter is reported for the first time to drive the expression of green fluorescent protein in S. oneidensis MR-1. Based on the same vector, the Mtr pathway genes mtr A, mtr C, and mtr CAB were also successfully expressed in MR-1. The recombinant strains had higher ferric reductase activity compared to the wild type. The highest enzymatic activity of 508.33 U/L in genetic Shewanella with mtr C gene is obtained, which is 1.53-fold higher than that of wild strain. The plasmids were stable up to 90 generations. Conclusion We have demonstrated an expression system based on pLacI promoter and rep B ori in Shewanella . Consequently, the combination of rep B and pLacI will have great potential in Shewanella to turn on expression of different genes constitutively.