The characterization and quantification of methanotrophic bacterial populations in constructed wetland sediments using PCR targeting 16S rRNA gene fragments

Three mesocosms were studied to evaluate the effect of wetland plants on the methanotrophic bacterial populations in the sediments of a full-scale constructed wetland. Cores were collected from two vegetated mesocosms and one unvegetated mesocosm from fall 2002 through summer 2003. Competitive quantitative PCR revealed no significant differences in the quantities of either Type I or Type II methanotrophic bacteria between the vegetated and unvegetated mesocosms. Type I methanotroph-biased nested PCR-DGGE resulted in the detection of 23 different populations related to Methylococcus, Methylomonas, Methylobacter, Methylocaldum, and Methylosarcina spp. Type II methanotroph-biased nested PCR-DGGE resulted in the detection of 5 different populations, more than 90% of which were related to previously uncultivated Type II methanotrophs. While wetland vegetation did not affect the structure of either the Type I or Type II methanotrophic communities, the Type I methanotrophic community structure was observed to vary seasonally. This work suggests that wetland plants neither enhanced nor adversely affected the size or structure of methanotrophic communities in our constructed wetland. Substantial quantities of both Type I and Type II methanotrophic populations were detected in both planted and unplanted mesocosms, suggesting that the constructed wetland had substantial potential for xenobiotic bioremediation whether or not plants were present.