Abstract
- Anaerobic ammonium oxidation (anammox) is the microbial N removal pathway of NH4+ oxidation coupled to NO2- reduction, and is mediated by bacteria belonging to the phylum Planctomycetales. Microbial diversity and ecology of anammox bacteria have not yet been fully revealed due to limitations of 16S rDNA analysis. The hydrazine oxidase gene in cluster 1 (hereafter hzoA/hzoB) was suggested as a proper genetic marker due to its high expression and ubiquitous presence in anammox bacteria. We conducted a comparative analysis of 16S rDNA and hzoA/hzoB genes to reveal anammox bacterial diversity and distribution in various aquatic environments. Phylogenetic analyses of 16S rDNA and hzoA/hzoB genes showed the dominance of Scalindua organisms in marine ecosystems, but there was no congruence of 16S rDNA and hzoA/hzoB gene phylogenies among the freshwater anammox bacteria associated with Brocadia sp., Jettenia sp., and Anammoxoglobus sp. Much higher diversity of anammox bacteria was revealed based on hzoA/hzoB genes than 16S rDNA in the examined environments. The highest diversity was observed in deep-sea sediments where only Scalindua sequences were detected. Thus, molecular detection and resulting phylogeny of the hzoA/hzoB gene generated a more complete understanding of anammox bacterial diversity and their ecological distribution in various aquatic ecosystems.