Combined genomics and experimental analyses of respiratory characteristics of Shewanella putrefaciens W3-18-1.

It has previously been shown that the Shewanella putrefaciens W3-18-1 strain produces remarkably high current in microbial fuel cells (MFCs) and can form magnetite at 0°C. To explore the underlying mechanisms, we developed a genetic manipulation method by deleting the restriction-modification system genes of the SGI1 (Salmonella genome island 1)-like prophage and analyzed the key genes involved in bacterial respiration. W3-18-1 has less respiratory flexibility than the well-characterized S. oneidensis MR-1 strain, as it possesses fewer cytochrome c genes and lacks the ability to oxidize sulfite or reduce dimethyl sulfoxide (DMSO) and timethylamine oxide (TMAO). W3-18-1 lacks the hydrogen-producing Fe-only hydrogenase, and the hydrogen-oxidizing Ni-Fe hydrogenase genes were split into two separate clusters. Two periplasmic nitrate reductases (NapDAGHB and NapDABC) were functionally redundant in anaerobic growth of W3-18-1 with nitrate as the electron acceptor, though napDABC was not regulated by Crp. Moreover, nitrate respiration started earlier in W3-18-1 than in MR-1 (with NapDAGHB only) under microoxic conditions. These results indicate that Shewanella putrefaciens W3-18-1 is well adapted to habitats with higher oxygen levels. Taken together, the results of this study provide valuable insights into bacterial genome evolution.