"Candidatus Methanoperedens nitroreducens" is an archaeon that couples the anaerobic oxidation of methane to nitrate reduction. In natural and manmade ecosystems, this archaeon is often found at oxic-anoxic interfaces where nitrate, the product of aerobic nitrification, cooccurs with methane produced by methanogens. As such, populations of "Ca. Methanoperedens nitroreducens" could be prone to regular oxygen exposure. Here, we investigated the effect of 5% (vol/ vol) oxygen exposure in batch activity assays on a "Ca. Methanoperedens nitroreducens" culture, enriched from an Italian paddy field. Metagenome sequencing of the DNA extracted from the enrichment culture revealed that 83% of 16S rRNA gene reads were assigned to a novel strain, "Candidatus Methanoperedens nitroreducens Verserenetto." RNA was extracted, and metatranscriptome sequencing upon oxygen exposure revealed that the active community changed, most notably in the appearance of aerobic methanotrophs. The gene expression of "Ca. Methanoperedens nitroreducens" revealed that the key genes encoding enzymes of the methane oxidation and nitrate reduction pathways were downregulated. In contrast to this, we identified upregulation of glutaredoxin, thioredoxin family/like proteins, rubrerythrins, peroxiredoxins, peroxidase, alkyl hydroperoxidase, type A flavoproteins, FeS cluster assembly protein, and cysteine desulfurases, indicating the genomic potential of "Ca. Methanoperedens nitroreducens Verserenetto" to counteract the oxidative damage and adapt in environments where they might be exposed to regular oxygen intrusion.
- "Candidatus Methanoperedens nitroreducens"
- Anaerobic oxidation of methane
- NC10 phylum bacteria
- Oxidative stress