Reduction of Trimethylamine Oxide by Bacterial Enzymes

Abstract

The trimethylamine oxide reducing enzyme systems of several common bacteria were found to have the following characteristics: (1) They are sensitive to acid conditions, showing progressively decreased activity as the pH is lowered from 8.0 to 6.0. Below pH 6.0 the system was relatively inert. (2) The activity also decreased with reductions in temperature between 37° and 0 °C., but even at 0 °C. the trimethylamine oxide is slowly reduced. (3) Increased sodium chloride decreased the rate of the enzyme activity. For the common non-halophilic species, concentrations of sodium chloride between 7 and 9 per cent almost totally inhibited the enzyme activity. (4) Nitrite inhibited the oxide reducing activity of the enzyme systems of all the organisms that were tested, but with varying decreases of inhibition with different species. Nitrate inhibited the activity of some species but not of others. (5) Within this general picture, there are slight differences which appear to be characteristic of bacterial species. The two species which were isolated from fish, Ps. putrefaciens and Achromobacter #176 were more sensitive than E. coli or A. aerogenes to reductions in pH between 7.0 and 6.0. E. coli, A. aerogenes and Ps. putrefaciens were strongly inhibited by sodium nitrate while S. marcescens and Achromobacter #176 were not. There is also considerable difference in the capacity of cells of different bacterial species to reduce trimethylamine oxide. Cultures of Achromobacter and non-fluorescent Pseudomonas were the most active of those tested.