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Bacterial communities in a tar-contaminated lake sediment
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)
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)
(Department of Cell and Molecular Biology, Biomedical Centre Uppsala University, Sweden)
(Department of Environmental Microbiology, Helmholtz Centre for Envi-ronmental Research – UFZ, Microbial Ecosystem Services Group, Leipzig, Germany)
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Organic anthropogenic pollutants, such as polycyclic aromatic hydrocarbons (PAHs) are widespread in nature and even low concentrations can be harmful for many organisms. To assess if also microbiota residing in freshwater sediments respond to such contaminants a lake sediment adjacent to the former discharge of a factory that conducted tar distillation in the early 20th century in central Sweden were studied. We compared the bacterial community composition (BCC) at sites affected by high tar loads to BCC in a linked, but pristine sediment, and a downstream site that is likely influenced by regular diffusive loads of PAHs. PAH and VOC (Volatile Organic Carbon) concentrations were analyzed whereas sediment aliquots were used for molecular identification of the local BCC. Here we took the opportunity to compare the bacteria abundance-data retrieved from two distinct approaches; two OTU tables were generated based on either paired-end MiSeq Illumina 16S rRNA gene amplicon sequencing or direct HiSeq Illumina-based metagenome sequencing of sediment DNA extracts. Both methods revealed that the high PAH loads adjacent to the tar factory significantly alters the BCC compared to the less affected sites, even though they both partly result in contrasting outcome. The highly contaminated sediments hosted a bacterial community that was low in richness, featuring taxa known to colonize habitats with high PAH loads. For instance the relative abundance of Sphingomonadales and Burkhoderiales, both orders, within the phylum Proteobacteria, increased relative to the pristine site as well as Acidimicrobiales, one subclass of Actinobacteria. Interestingly the sediment downstream of the former factory outlet was colonized by bacteria which were very similar in community composition to the pristine site upstream of the factory outlet, implying a capacity of the natural sediment microbiota to cope with low levels of PAH contamination. 

National Category
Microbiology
Research subject
Biology with specialization in Microbiology
Identifiers
URN: urn:nbn:se:uu:diva-229140OAI: oai:DiVA.org:uu-229140DiVA: diva2:735859
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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1157
Keyword
bacteria, environmental filtering, diversity, ecosystem service, hydrocarbon utilization, Southern Ocean, sediment
National Category
Natural Sciences Biological Sciences
Research subject
Biology with specialization in Microbiology
Identifiers
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)
Opponent
Supervisors
Available from: 2014-08-26 Created: 2014-08-01 Last updated: 2014-09-08

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