Impact of the contemporary environment on denitrifying bacterial communities

•Fields, bioreactors, and wetlands showed distinct bacterial communities.•The bioreactor communities were more similar to wetlands than to fields.•The contemporary environment had more influence than legacy effects or immigration.

To engineer a microbial ecosystem, an understanding of the relative influence of legacy effects versus the contemporary environment on the microbial community is required. In this work, the influence of these factors on both the denitrifying bacterial community structure and the overall bacterial community structure was assessed through comparison of agricultural soils, denitrifying bioreactors, and natural and constructed wetlands. Terminal restriction fragment analysis (tRFLP) of the nosZ gene and automated ribosomal intergenic spacer analysis (ARISA) were used. The results suggest distinct communities are characteristic of soil, bioreactors, and wetlands and show a strong influence of the contemporary environment on the bacterial and denitrifying bacterial communities in the bioreactors.

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