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Response and effect interactions between bacterial communities and organic matter
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Applied Microbiology and Biotechnology Laboratory, Department of Botany, University of Delhi.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology. Catalan Institute for Water Research (ICRA).
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The interaction between bacteria and dissolved organic matter (DOM) is crucial for the global carbon cycling. Despite decades of research there are, however, few consistent patterns regarding the relationship between bacterial diversity and community composition and DOM. Here we hypothesized that one reason for such inconsistences among studies is that bacterial communities can adapt to a DOM source over time, whereby a change in the functioning of a community can be, at least partly, decoupled from its composition and diversity. To test this idea we performed a reciprocal transplant experiment with medium (i.e. DOM source) and bacterial communities from two boreal lakes. In this experiment the two communities were allowed to adapt to their indigenous and their foreign source of DOM over 42 days. Bacterial community composition (BCC) was measured throughout the experiment. In addition we measured the capacity of the communities to use DOM, in repeated short (5 days) separated bioassays. The results show a response of bacterial community composition to the DOM sources which was influenced by the origin of the community. In contrast, we could not show an effect of BCC on DOM-processing and functional performance. Indeed, communities of different origin processed the two DOM sources equally well even at the beginning of the experiment. This work demonstrates that the DOM pool can be a strong selective force for BCC but not vice versa. 

National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-331696OAI: oai:DiVA.org:uu-331696DiVA: diva2:1149752
Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2017-10-23
In thesis
1. Extent and limitations of functional redundancy among bacterial communities towards dissolved organic matter
Open this publication in new window or tab >>Extent and limitations of functional redundancy among bacterial communities towards dissolved organic matter
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the key processes in the carbon cycle on our planet is the degradation of dissolved organic matter (DOM) in aquatic environments. The use of organic matter by bacteria links energy from DOM to higher trophic levels of the ecosystem when bacteria are consumed by other organisms. This is referred to as the microbial loop. In this thesis I examined if the communities were functionally redundant in their ability to utilize organic matter, or if variation in bacterial composition and richness is of importance. To test this overarching question several experiments were conducted that include methods such as illumina sequencing of the 16S rRNA gene for taxonomic identification of bacterial communities, flow cytometry to follow the growth of communities and spectroscopic measurement to describe the composition of the organic matter pool. Initially we demonstrated how to optimally sterilize organic matter for experimental studies in order to preserve its natural complexity. In further experiments we found that bacterial communities are redundant in their utilization of organic matter and can maintain optimal performance towards a range of organic matter pools. Related to this we found that pre-adaptation to organic matter played a small role as communities performed equally well regardless of their environmental history. We saw a small effect of richness and composition of bacterial communities on the efficiency of organic matter use, but conclude that this is of minor importance relative to abiotic factors. Still, we also show that organic matter can put strong selection pressure on bacterial communities with regards to richness and composition. Additionally we found that the supply rate of a carbon compound greatly influenced the energy utilization of the compound, i.e. a higher growth rate can be maintained if substrate is delivered in pulses relative to a continuous flow. Finally we conclude that the variation in bacterial communities is unlikely to have a major influence on carbon cycling in boreal lakes, but to enable a finer understanding, the genetics underlying the carbon utilization needs to be further explored. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 41 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1578
Keyword
Dissolved organic matter, BCC, biodiversity, functional redundancy
National Category
Natural Sciences
Research subject
Microbiology
Identifiers
urn:nbn:se:uu:diva-331772 (URN)978-91-513-0112-9 (ISBN)
Public defence
2017-12-01, Friessalen, Norbyvägen 18, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2017-11-08 Created: 2017-10-17 Last updated: 2017-11-08Bibliographically approved

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