Diversity of archaea and eubacteria in a constructed wetland in California

Wetlands harbor microorganisms that make significant contributions to global warming. In the anoxic niche, methanogens and sulfate-reducing bacteria (SRB) compete for the same substrates. Although approaches have been developed to study microbial diversity in natural wetlands, knowledge of the microbial diversity of constructed wetlands is scarce. This study was conducted to survey the eubacterial and archaeal diversities in a constructed wetland and to establish the functional groups of methanogens and SRB predominant under disturbance and restoration conditions. Phylogenetic analyses of the 16S rRNA gene indicated that the archaeal community was dominated by members of the phylum Crenarchaeota and that the eubacterial community was dominated by the phylum Proteobacteria. A difference in the diversity of the microbial communities from an agriculturally polluted input zone and a downstream natural site was observed. A small number of sequences corresponded to methanogens and SRB. Non-acetoclastic methanogenesis appeared to be the dominant methanogenic pathway, and SRB were either complete or incomplete acetate oxidizers. Novel groups of both methanogens and SRB may exist in this wetland.