Decoding the interspecies interaction in anammox process with inorganic feeding through metagenomic and metatranscriptomic analysis

There is increasing interest to understand the interspecies interactions between microbes of anaerobic ammonium oxidation (anammox) consortia. However, the microbial nitrogen and carbon interactions in inorganic suspended growth anammox consortia are still elusive. Here, we operated a long-term Continuous Stirred Tank Reactor (CSTR) with synthetic inorganic wastewater, which achieved 80% of total nitrogen removal at the steady-state, representing a nitrogen removal rate (NRR) of 1.032 kg-N/(m3·d). Our meta-omics analyses yielded 16 high-quality draft genomes and reconstructed their potential metabolic pathways. Elevated expressions of gene transcripts encoding for enzymes involved in nitrogen and carbon metabolisms were detected in isolates obtained from the same anammox consortia, suggesting their potential metabolic roles and possible microbial interaction capacity in anammox consortia. The expressed genes encoding NO support, nitrite/ammonium loop, dissimilatory nitrate reduction to ammonium, and denitrification in anammox bacteria, and its symbiotic bacteria could have benefits to the bacterial survival and reactor performance. The Carbohydrate-active enzyme analysis revealed that carbohydrate cross-feeding in autotrophic anammox consortia might shift the microbial community. Proteobacteria and anammox bacteria might contribute acetate and glycogen for other symbiotic microorganisms to support their survival. Proteobacteria-affiliated bacteria encoded the potentials of biotin synthesis, hinting at the possibility of the regulation of the diversity of the microbial community. The observed microbial interactions in anammox consortia with inorganic feeding facilitate the purification of anammox bacteria and their engineering application. [Display omitted] •“Ca. Brocadia sp.” dominant the microbial community without organics feeding.•Nitrogen removal was contributed by “Ca. Brocadia sp.” and its symbiotics.•Microbial C/N interactions were verified in anammox consortia without organic feeding.•Interspecies interaction suggests the accumulation of heterotrophic bacteria.•Biotin exchange plays a core role in the regulation of the microbial community.