Inability ofmenmutants ofEscherichia colito use trimethylamine-N-oxide as an electron acceptor

Mutants of Escherichia coli blocked in the biosynthesis of menaquinone were unable to use trimethylamine-N-oxide as an electron acceptor in complex medium containing glucose. Trimethylamine-N-oxide reduction and the consequent in-crease in growth could be restored in a menC mutant by either o-succinylbenzoic acid (OSB) or 1,4-dihydroxy-2-naphthoic acid (DHNA). In the case of a menB mutant, growth could not be restored by OSB; but addition of DHNA resulted in the restoration of growth to the full extent. These results are consistent with the metabolic blocks in the respective men mutants.