Genome-Centered Metagenomics Analysis Reveals the Symbiotic Organisms Possessing Ability to Cross-Feed with Anammox Bacteria in Anammox Consortia

Although using anammox communities
for efficient wastewater treatment
has attracted much attention, the pure anammox bacteria are difficult
to obtain, and the potential roles of symbiotic bacteria in anammox
performance are still elusive. Here, we combined long-term reactor
operation, genome-centered metagenomics, community functional structure,
and metabolic pathway reconstruction to reveal multiple potential
cross-feedings during anammox reactor start-up according to the 37
recovered metagenome-assembled genomes (MAGs). We found Armatimonadetes
and Proteobacteria could contribute the secondary metabolites molybdopterin
cofactor and folate for anammox bacteria to benefit their activity
and growth. Chloroflexi-affiliated bacteria encoded the function of
biosynthesizing exopolysaccharides for anammox consortium aggregation,
based on the partial nucleotide sugars produced by anammox bacteria.
Chlorobi-affiliated bacteria had the ability to degrade extracellular
proteins produced by anammox bacteria to amino acids to affect consortium
aggregation. Additionally, the Chloroflexi-affiliated bacteria harbored
genes for a nitrite loop and could have a dual role in anammox performance
during reactor start-up. Cross-feeding in anammox community adds a
different dimension for understanding microbial interactions and emphasizes
the importance of symbiotic bacteria in the anammox process for wastewater
treatment.