Nationwide metagenome survey of anammox processes via high-throughput next generation sequencing (NGS): 2012-2013

Anaerobic ammonium oxidation (anammox) process represents a promising approach for energy-efficient nitrogen turnover from side-stream and main-stream wastewater treatment plants (WWTPs). The study was conducted for the comparative metagenomic survey in taxonomic groups and functional gene clusters of the 13 samples from anammox-enriched wastewater treatment systems with different operating conditions, system configurations, and influent characteristics. In addition to survey, we report the discovery of anammox-enriched red granules unintentionally fostered in the anoxic zone of the full-scale nitritation-denitritation system. High-throughput shotgun metagenome sequencing using bench-top semi-conductor sequencing technology was able to retrieve a total of 991 Mbp of nucleotide sequence. The results showed highly assigned taxa among bacteria were Nitrosomonas and C. Kuenenia, demonstrating unique but still complex community structure. Whereas, marginal reads were assigned to nitrite oxidizing bacteria (NOB) in all but nitritationanammox system treating low strength wastewater due to favorable conditions for NOB. In parallel, functional profiles were determined using user-defined BLASTDB with selected genes regarding nitrogen transformation and carbon assimilation. The result provides the highly quantitative levels of hydrazine synthase (hzs), nitrate reductase (nar) and ammonia transporter (amt) gene annotations from the metagenome dataset. The study provided insights of taxonomic and functional structure of bacterial communities from different anammox-enriched systems. Further, the study acknowledged urgent need of anammox bacteria reference genome database to address reliable quantitative metagenome analysis in the anammoxenriched systems.