Effects of copper on the abundance and diversity of ammonia oxidizers during dairy cattle manure composting

- Potential ammonia oxidation values were inhibited significantly by Cu addition.
- Cu at 50 and 500 mg kg−1 inhibited amoA gene abundance in cattle manure compost.
- Cu may affect the AOA and AOB community structure and diversity.

This study investigated the effects of adding Cu(II) at two exposure levels (50 and 500 mg kg−1, i.e., Cu50 and Cu500 treatments, respectively) on the activity of ammonia-oxidizing microorganisms during dairy cattle manure composting. The results showed that the pH, NH4+-N, NO3−-N, and potential ammonia oxidation values were inhibited significantly by the addition of Cu(II). Furthermore, the abundances of the ammonia-oxidizing archaea (AOA) amoA gene and ammonia-oxidizing bacteria (AOB) amoA gene were determined by quantitative PCR, and their compositions were evaluated by denaturing gradient gel electrophoresis (DGGE). AOA was the dominant ammonia oxidizing microorganism, of which the abundance was much higher than AOB during composting. Cu50 and Cu500 had significant inhibitory effects on the abundance of the amoA gene. The DGGE profile and statistical analysis showed that Cu(II) changed the AOA and AOB community structure and diversity, where Nitrosomonas and Crenarchaeota dominated throughout the composting process.