Responses of Ammonia-Oxidizing Archaea and Bacteria in Malodorous River Sediments to Different Remediation Techniques

In this study, the joint use of high throughput sequencing, real-time quantitative PCR, and ammonia-oxidizing bacteria (AOB)-inhibiting allylthiourea was used to differentiate between the contributions of ammonia-oxidizing archaea (AOA) vs AOB to ammonia oxidation and ascertain how AOA and AOB responded to two widely used river remediation techniques (aeration and Ca(NO3)(2)injection). Results showed that ammonia oxidation was largely attributed to ATU-sensitive AOB rather than AOA andNitrosomonaswas the predominant AOB-related genus (53.86%) in the malodorous river. The contribution of AOB to ammonia oxidation in the context of aeration and Ca(NO3)(2)injection was 75.51 +/- 2.77% and 60.19 +/- 10.44%, respectively. The peak of AOB/AOA ratio and the marked increase of relative abundances ofNitrosomonasandNitrosospirain aeration runs further demonstrated aeration favored the ammonia oxidation of AOB. Comparatively, Ca(NO3)(2)injection could increase the ammonia oxidation contribution of AOA from 31.32 +/- 6.06 to 39.81 +/- 10.44% and was significantly correlated withNitrosococcusof AOB (r = 0.796,p < 0.05),Candidatus_Nitrosopelagicusof AOA (r = 0.986,p < 0.01), and AOA Simpson diversity (r = - 0.791,p < 0.05). Moreover,Candidatus_Nitrosopelagicuswas only present in Ca(NO3)(2)runs. Taken together, Ca(NO3)(2)was recognized as an important factor in mediating the growth and ecological niches of ammonia oxidizers. Graphical abstract

Automated summary

The study used high throughput sequencing, real-time quantitative PCR, and allylthiourea to differentiate between the contributions of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) to ammonia oxidation. Results showed that AOB were the major contributors to ammonia oxidation, with Nitrosomonas being the predominant genus. Aeration favored AOB ammonia oxidation, while Ca(NO3)(2) injection increased AOA contribution and influenced the growth of ammonia oxidizers.