Interactions and responses of n-damo archaea, n-damo bacteria and anammox bacteria to various electron acceptors in natural and constructed wetland sediments

Anaerobic methane oxidizing organisms, including sulfate dependent archaea (SAMO), nitrite dependent bacteria (n-damo), and nitrate archaea (n-damo), may collaborate with anaerobic ammonia oxidizers (anammox) bacteria in wetlands to remove inorganic nitrogen. The objective was to examine the structure and abundance of these organisms and their response to substrate inputs (sulfate, nitrate, or nitrite) in two wetlands of contrasting properties: a natural wetland and a constructed wetland to treat swine manure. No SAMO archaea were detected in either wetland. For n-damo bacteria, Ca. Methylomirabilis oxyfera dominated the natural wetland, while Clade 2 dominated the constructed wetland. For n-damo archaea, Clade 1 dominated the constructed wetland, while Clade 3 dominated the natural wetland. For anammox bacteria, Ca. Brocadia dominated both the natural wetland and the constructed wetland. Generally, the natural wetland contained higher gene abundance and more diversity of these three microorganisms than the constructed wetland, which could be due to high ammonium concentrations in the constructed wetland, forcing selections of genotypes to a narrow range of microorganisms. A slurry incubation experiment showed that both n-damo archaea and anammox bacteria increased over time in the constructed wetland sediment, indicating these two microorganisms might cooperate to complete the denitrification process from nitrate to dinitrogen gas.