Fimbriimonadales performed dissimilatory nitrate reduction to ammonium (DNRA) in an anammox reactor

Hoang Phuc Trinh; Sang-Hoon Lee; Na-Kyung Kim; Thi Vinh Nguyen; Hee-Deung Park

doi:10.1016/j.watres.2024.122575

Fimbriimonadales performed dissimilatory nitrate reduction to ammonium (DNRA) in an anammox reactor

Water Res. 2024 Oct 3;268(Pt A):122575. doi: 10.1016/j.watres.2024.122575. Online ahead of print.

Authors

Hoang Phuc Trinh¹, Sang-Hoon Lee¹, Na-Kyung Kim², Thi Vinh Nguyen¹, Hee-Deung Park³

Affiliations

¹ School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, South Korea.
² Department of Animal Science, College of Agricultural, Consumer, and Environmental Science, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
³ School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 02841, South Korea; KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, South Korea. Electronic address: heedeung@korea.ac.kr.

PMID: 39383805
DOI: 10.1016/j.watres.2024.122575

Abstract

Bacteria belonging to the order Fimbriimonadales are frequently detected in anammox reactors. However, the principal functions of these bacteria and their potential contribution to nitrogen removal remain unclear. In this study, we aimed to systematically validate the roles of Fimbriimonadales in an anammox reactor fed with synthetic wastewater. High-throughput 16S rRNA gene sequencing analysis revealed that heterotrophic denitrifying bacteria (HDB) were the most abundant bacterial group at the initial stage of reactor operation and the abundance of Fimbriimonadales members gradually increased to reach 38.8 % (day 196). At the end of reactor operation, Fimbriimonadales decreased to 0.9 % with an increase in anammox bacteria. Correlation analysis demonstrated nitrate competition between Fimbriimonadales and HDB during reactor operation. Based on the phylogenetic analysis, the Fimbriimonadales sequences acquired from the reactor were clustered into three distinct groups, which included the sequences obtained from other anammox reactors. Metagenome-assembled genome analysis of Fimbriimonadales allowed the identification of the genes narGHI and nrfAH, responsible for dissimilatory nitrate reduction to ammonium (DNRA), and nrt and nasA, responsible for nitrate and nitrite transport. In a simulation based on mass balance equations and quantified bacterial groups, the total nitrogen concentrations in the effluent were best predicted when Fimbriimonadales was assumed to perform DNRA (R² = 0.70 and RMSE = 18.9). Moreover, mass balance analysis demonstrated the potential contribution of DNRA in enriching anammox bacteria and promoting nitrogen removal. These results prove that Fimbriimonadales compete with HDB for nitrate utilization through DNRA in the anammox reactor under non-exogenous carbon supply conditions. Overall, our findings suggest that the DNRA pathway in Fimbriimonadales could enhance anammox enrichment and nitrogen removal by providing substrates (nitrite and/or ammonium) for anammox bacteria.

Keywords: Anammox; Dissimilatory nitrate reduction to ammonium; Fimbriimonadales; Metagenome-assembled genome.