Dimethyl sulfoxide reductase is not required for trimethylamine N-oxide reduction inEscherichia chcoli

Deletion mutants of Escherichia coli lacking dimethyl sulfoxide (DMSO) reductase activity and consequently unable to utilize DMSO as an electron acceptor for anaerobic growth have been isolated. These mutants retained the ability to use trimethylamine N-oxide (TMAO) as an electron acceptor and the TMAO reductase activity was found to be unaltered. Heating the cell-free extract of the wild-type strain at 70°C for 15 min selectively inactivated the DMSO reductase activity while the TMAO reductase activity remained unchanged for at least 1 h.