AUTHOR=Shah Anish S. , Hsu Pei-Chun , Chisholm Chris , Podolyan Andriy , Cameron Keith , Luo Jiafa , Stenger Roland , Carrick Sam , Hu Wei , Ferguson Scott A. , Wei Wenhua , Shen Jupei , Zhang Limei , Liu Hongbin , Zhao Tongke , Wei Wenxue , Ding Weixin , Pan Hong , Liu Yimeng , Li Bowen , Du Jianjun , Di Hong J. 

TITLE=Nitrification inhibitor chlorate and nitrogen substrates differentially affect comammox Nitrospira in a grassland soil

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1392090

DOI=10.3389/fmicb.2024.1392090

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>Through the combined use of two nitrification inhibitors, Dicyandiamide (DCD) and chlorate with nitrogen amendment, this study aimed to investigate the contribution of comammox <italic>Nitrospira</italic> clade B, ammonia oxidizing bacteria (AOB) and archaea (AOA) to nitrification in a high fertility grassland soil, in a 90-day incubation study.</p></sec><sec><title>Methods</title><p>The soil was treated with nitrogen (N) at three levels: 0 mg-N kg<sup>-1</sup> soil, 50 mg-N kg<sup>-1</sup> soil, and 700 mg-N kg<sup>-1</sup> soil, with or without the two nitrification inhibitors. The abundance of comammox <italic>Nitrospira</italic>, AOA, AOB, and nitrite oxidising bacteria (NOB) was measured using qPCR. The comammox Nitrospira community structure was assessed using Illumina sequencing.</p></sec><sec><title>Results and Discussion</title><p>The results showed that the application of chlorate inhibited the oxidation of both NH<sub>4</sub><sup>+</sup> and NO<sub>2</sub><sup>-</sup> in all three nitrogen treatments. The application of chlorate significantly reduced the abundance of comammox <italic>Nitrospira amo</italic>A and <italic>nxr</italic>B genes across the 90-day experimental period. Chlorate also had a significant effect on the beta diversity (Bray-Curtis dissimilarity) of the comammox <italic>Nitrospira</italic> clade B community. Whilst AOB grew in response to the N substrate additions and were inhibited by both inhibitors, AOA showed litle or no response to either the N substrate or inhibitor treatments. In contrast, comammox <italic>Nitrospira</italic> clade B were inhibited by the high ammonium concentrations released from the urine substrates. These results demonstrate the differential and niche responses of the three ammonia oxidising communities to N substrate additions and nitrification inhibitor treatments. Further research is needed to investigate the specificity of the two inhibitors on the different ammonia oxidising communities.</p></sec>