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bioRxiv · 10.64898/2026.07.05.735045

Horizontal gene transfer drives DNRA capacity in wastewater treatment systems

Wang, C.·Gao, M.·Qiu, N.·Ding, X.·Song, P.
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Abstract

Anammox bacteria require large amounts of iron for hydrazine synthase (HZS) and hydrazine oxidoreductase (HZO). By analyzing 8 anammox genomes across four genera, we found that only Candidatus Brocadia sinica harbors a compact genomic island (<10 kb) where hzs co-localizes with iron uptake (TonB, FeoAB) and Fe-S cluster assembly (NifU/NifS) genes. All other species show dispersed architectures (>100 kb separation). In the dispersed species Ca. Kuenenia stuttgartiensis, transcriptomic data revealed a 300- to 1500-fold excess of hzs over iron genes, indicating severe expression uncoupling. Thus, physical co-localization of iron support genes with anammox core enzymes is rare but exists in one Brocadia lineage, potentially enabling better co-regulation. These findings provide a genomic basis for predicting iron responsiveness across anammox species in engineered systems. Significance StatementOnly Candidatus Brocadia sinica harbors a compact <10 kb iron-nitrogen genomic island. All other anammox species show dispersed iron-nitrogen architectures (>100 kb separation). Dispersed species exhibit 3001500-fold expression mismatch between hzs and iron genes. Physical co-localization may enable co-regulation of iron supply with anammox metabolism. Genomic architecture predicts lineage-specific iron responsiveness in anammox engineering.

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Wang, C., Gao, M., Qiu, N., Ding, X., Song, P.. 2026-07-06. Horizontal gene transfer drives DNRA capacity in wastewater treatment systems. https://doi.org/10.64898/2026.07.05.735045

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