The effect of water table fluctuation on microbial benzene utilization in a constructed wetland

• Microbial degradation of benzene in anoxic habitats is so low that it’s hardly detectable. In this study benzene-utilizing taxa residing in a mostly anoxic wetland were identified and visualized by applying single-cell techniques and phylogenetic identification based on 16S rRNA amplicon sequencing. We also tested whether cyclic water table fluctuations had a positive effect on benzene removal rates.We found that cyclic water table changes in a constructed wetland with horizontal water flow created fluctuations in redox conditions and resulted in an increase of microbial biomass. However, it did not enhance the removal of recalcitrant hydrocarbon contaminants, at least not within one year of operation. Benzene remained persistent, despite the increased microbial biomass. A slight decrease in ammonia and nitrate concentrations may hint towards an increase in microbial denitrification as a result of the artificially induced hydrodynamic changes.Despite the low benzene uptake rates, we successfully visualized and identified anaerobic benzene-degrading microbes, by using 14C-benzene-Microautoradiography (MAR) and Catalyzed Reporter Deposition Fluorescence in situ Hybridization (CARD-FISH) with a probe set targeting proposed anaerobic benzene-utilizers. We found Deltaproteobacteria, Firmicutes, Archaea and Azoarcus (Betaproteobacteria) to actively take up benzene anaerobicallyOur MAR-CARD-FISH protocol can be applied to visualize benzene- or other aromatic hydrocarbon-utilizing microbes in contaminated sediments and soils and can help to reveal physical associations of different taxa involved in the recalcitrant hydrocarbon break-down.

Subject headings

NATURVETENSKAP  -- Biologi -- Mikrobiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Microbiology (hsv//eng)

Keyword

constructed wetland

benzene

anoxic

bacteria

fluctuation

Publication and Content Type

vet (subject category)

ovr (subject category)