Effects of phenolic acids on ammonia oxidation by terrestrial autrotrophic nitrifying microorganisms
1991
McCarty, G.W. | Bremner, J.M. | Schmidt, E.L.
It has been hypothesized that vegetation in certain ecosystems inhibits nitrification in soil by producing phenolic compounds that inhibit oxidation of ammonia by nitrifying microorganisms. This hypothesis is based largely on a report that very low concentrations (10(-6) M-10(-8) M) of several phenolic acids (notably ferulic acid) completely inhibited NO2- production in an aqueous suspension of soil treated with (NH4)2SO4 and a nutrient solution suitable for growth of Nitrosomonas and other autotrophic nitrifying microorganisms. To evaluate this hypothesis, we determined the effects of three phenolic acids (ferulic acid, caffeic acid, and p-coumaric acid) on nitrite production by representatives of three genera of terrestrial autotrophic nitrifying microorganisms (Nitrosospira, Nitrosomonas, or Nitrosolobus) grown on a defined medium containing NH4+. We found that nitrite production by the Nitrosospira was not inhibited by ferulic acid, caffeic acid, or p-coumaric acid at concentrations of 10(-6) or 10(-5) M and was only slightly inhibited when these acids were at a concentration of 10(-4) M. We also found that ferulic acid did not markedly inhibit nitrite production by the three genera of nitrifying microorganisms studied, even when its concentration was as high as 10(-3) M. These observations invalidate the hypothesis tested because the phenolic acids studied did not significantly retard ammonia oxidation by autotrophic microorganisms even when their concentration in cultures of these microorganisms greatly exceeded their concentrations in soils.
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