Growth and N2O production of Nitrosocosmicus clade in agricultural soil when responding to high ammonium inputs

PurposeIn recent years, some ammonia-oxidizing archaea (AOA) species from the Nitrosocosmicus clade have been suggested to be ammonium tolerant, with ability close to many ammonia-oxidizing bacteria (AOB) species. However, the Nitrosocosmicus clade growth and contribution to N2O production in agricultural soil when responding to high ammonium inputs are still unknown.MethodsBased on three microcosms, the effects of ammonium inputs on the abundance of Nitrosocosmicus clade in AOA community, the Nitrosocosmicus clade growth, and contribution to N2O production were investigated. Based on batch cultivation of Candidatus Nitrosocosmicus agrestis (Ca. N. agrestis) and the microcosm with extra addition of Ca. N. agrestis, AOA contribution to N2O production was studied.ResultsHigh ammonium inputs benefited the abundance increase of Nitrosocosmicus clade, with relative abundance increased from 2.6 to 9.1-15.5% of the AOA community in DNA samples, and from 1.4 to 15.1-47.5% in RNA samples. High ammonium inputs promoted the growth of Nitrosocosmicus clade, with number accounting for 16.9-22.9% of the total AOA but 48.5-74.2% of the increased AOA. High ammonium inputs also activated the expression of Nitrosocosmicus clade amoA gene. Due to the presence of Nitrosocosmicus clade, high ammonium inputs increased the contribution of AOA to N2O production; in the presence of Ca. N. agrestis, the contribution of AOA to N2O production is comparable to AOB when responding to high ammonium inputs.ConclusionThe Nitrosocosmicus clade in agricultural soils is likely ammonium tolerant; its growth and contribution to N2O production could be favored by high ammonium inputs.

Automated summary

Recent research suggests that some species from the Nitrosocosmicus clade of ammonia-oxidizing archaea (AOA) may have ammonium tolerance similar to many ammonia-oxidizing bacteria (AOB) species. The growth of Nitrosocosmicus clade and its contribution to N2O production in agricultural soil under high ammonium inputs were investigated.