Trimethylamine-N-oxide (TMA-0) reductase activity of resting cells of Escherichia coli was inhibited by tetrasodium ethylenediaminetetraacetate (Na₄EDTA), benzoic acid (BA), and methylparaben (MP). The 50% inhibitory concentrations of Na₄EDTA, BA, and MP were 20.2, 1.2, and 32.4 mM, respectively. BA at pH 6.5 or below most effectively inhibited the TMA-0 reductase. Sorbic acid (SA), up to 0.70 mM, had no effect on TMA-0 reductase activity, but SA inhibited the growth and subsequent TMA production in E. coli at or above 0.35 mM. / Graduation date: 1981