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The effect of water table fluctuation on microbial benzene utilization in a constructed wetland
Department of Environmental Microbiology, Helmholtz Centre for Environmental Research – UFZ, Microbial Ecosystem Services Group, Leipzig, Germany. (Department of Ecology and Genetics, Limnology Uppsala University, Uppsala, Sweden)
Science for Life Laboratory Uppsala, Sweden. (Department of Ecology and Genetics, Limnology, Uppsala University, Uppsala, Sweden)
(Department of Environmental Microbiology, Helmholtz Centre for Envi-ronmental Research – UFZ, Microbial Ecosystem Services Group, Leipzig, Germany)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

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 anaerobically

Our 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.

Keyword [en]
constructed wetland, benzene, anoxic, bacteria, fluctuation
National Category
URN: urn:nbn:se:uu:diva-229139OAI: oai:DiVA.org:uu-229139DiVA: diva2:735857
Available from: 2014-08-01 Created: 2014-08-01 Last updated: 2014-09-08
In thesis
1. Environmental filtering of bacteria in low productivity habitats
Open this publication in new window or tab >>Environmental filtering of bacteria in low productivity habitats
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Microbes fulfill important ecosystem functions by contributing as drivers of global nutrient cycles. Their distribution patterns are mainly controlled by environmental heterogeneities. So far, little is known about the mode of action of particular environmental drivers on the microbiota, particularly in low productivity habitats.

The aim of this thesis was to investigate the relationships between local environmental drivers and the microbial responses at the level of communities, individuals and realized function, using three structurally different model habitats sharing the feature of overall low productivity. Using a hypothesis-based approach and extensive 16S rRNA amplicon mapping of bacterioplankton colonizing the polar Southern Ocean, I identified how the seasonal formation of open-water polynyas and coupled phytoplankton production affected the diversity of surface bacterial communities and resulted in a cascading effect influencing the underlying dark polar water masses. Additional laboratory experiments, with cultures exposed to light, resulted in reduction in alpha diversity and promoted opportunistic populations with most bacterial populations thriving in the cultures typically reflected the dominants in situ.

Furthermore it was experimentally tested how induced cyclic water table fluctuations shaping environmental heterogeneity in a constructed wetland on temporal scale, by directly affecting redox conditions. Twelve months of water table fluctuations resulted in enhanced microbial biomass, however a shift in community composition did not lead to a significant increase in pollutant removal efficiency when compared to a static control wetland. I detected phyla that have previously been proposed as key players in anaerobic benzene break-down using a protocol that was developed for single cell activity screening using isotope-substrate uptake and microautoradiography combined with taxonomic identification based on fluorescent in situ hybridization targeting the 16S rRNA. Eventually, I provide an example of how anthropogenic pollution with polyaromatic hydrocarbons induced a strong environmental filtering on intrinsic microbial communities in lake sediments.

In conclusion, my studies reveal that microorganisms residing in low productivity habitats are greatly influenced by environmental heterogeneity across both spatial and temporal scales. However, such variation in community composition or overall abundance does not always translate to altered community function.


Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 44 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1157
bacteria, environmental filtering, diversity, ecosystem service, hydrocarbon utilization, Southern Ocean, sediment
National Category
Natural Sciences Biological Sciences
Research subject
Biology with specialization in Microbiology
urn:nbn:se:uu:diva-229144 (URN)978-91-554-8986-1 (ISBN)
Public defence
2014-09-16, Fries salen, Evolutionsbiologiskt centrum, EBC, Norbyvägen 18, 752 36 Uppsala, Uppsala, 10:00 (English)
Available from: 2014-08-26 Created: 2014-08-01 Last updated: 2014-09-08

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