EFFECT OF PICOLINIC-ACID (2-PYRIDINE CARBOXYLIC-ACID) ON THE OXIDATION OF METHANE AND AMMONIA IN SOIL AND IN LIQUID CULTURE

In cultures of Methylosinus trichosporium OB3b. picolinic acid strongly inhibited both methane oxidation (apparent K1 7.6μM) and nitrite production (apparent K1 3.8 μm). 2-chloro-6-methyl pyridine was relatively ineffective and nicotinic and isonicotinic acids had no effect. In slurries of a methane-enriched cultivated humisol, picolinic acid was less effective in inhibiting methane oxidation (apparent K1. 194μM). However, chemoautotrophic nitrification in ammonia-enriched slurries was not affected by up to 2 mM picolinic acid. The inhibition of methane oxidation in slurries by picolinic acid persisted for 42 h after which methane oxidation activity resumed. Evidence is provided that picolinic acid was degraded by an adapted flora, and that adaptation to nicotinic acid degradation conferred ability to degrade picolinic acid in a deciduous swamp soil but not in the humisol. It is concluded that picolinic acid may have some potential to differentially inhibit methanotrophic and chemoautotrophic nitrification. © 1990.