Long-term fertilization on ammonia oxidizers in Ultisols

Complete ammonia oxidizers (comammox) are recently discovered to be capable of ammonia oxidizing and nitrite oxidizing on their own, which refutes the long-held paradigm that nitrification required the activity of two distinct groups of microbes. However, the niche specialization of comammox and their co-occurrence with canonical ammonia oxidizers remains elusive in agricultural soils, especially considering aggregate fractionation. Here, we investigated the effect of 27 years application of mineral and/or organic fertilizer (rice straw, peanut straw, radish, or pig manure) on community structure and co-occurrence of comammox and canonical ammonia oxidizers in aggregates from an acidic Ultisol. The aim of this project was to (1) investigate how long-term mineral and organic fertilizations affect the community composition of AOA, AOB and comammox in aggregate sizes; (2) explore the niche differentiation and co-occurrence links involving AOA, AOB and comammox communities.