Effect of nitrification inhibitors on the growth and activity of Nitrosotalea devanaterra in culture and soil

The soil archaeon Nitrosotalea devanaterra is a representative of an abundant ammonia oxidising archaeal lineage. The effects of three nitrification inhibitors (allylthiourea (ATU), dicyandiamide (DCD) and nitrapyrin) on growth in both soil and liquid culture were compared. DCD and nitrapyrin inhibited nitrification at similar concentrations to bacterial ammonia oxidisers. Although DCD completely inhibited nitrification, some growth occurred in liquid cultures. Surprisingly, Nitrosotalea devanaterra was less susceptible to inhibition by ATU, which stimulated, rather than inhibited, nitrification in soil microcosms. Inhibition thresholds and responses may reflect differences in ammonia oxidation mechanisms between archaea and bacteria.