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Function-specific response to depletion of microbial diversity
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.
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.
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2011 (English)In: The ISME Journal, ISSN 1751-7362, Vol. 5, no 2, 351-361 p.Article in journal (Refereed) Published
Abstract [en]

Recent meta-analyses suggest that ecosystem functioning increases with biodiversity, but contradictory results have been presented for some microbial functions. Moreover, observations of only one function underestimate the functional role of diversity because of species-specific trade-offs in the ability to carry out different functions. We examined multiple functions in batch cultures of natural freshwater bacterial communities with different richness, achieved by a dilution-to-extinction approach. Community composition was assessed by molecular fingerprinting of 16S rRNA and chitinase genes, representing the total community and a trait characteristic for a functional group, respectively. Richness was positively related to abundance and biomass, negatively correlated to cell volumes and unrelated to maximum intrinsic growth rate. The response of chitin and cellulose degradation rates depended on the presence of a single phylotype. We suggest that species identity and community composition rather than richness matters for specific microbial processes.

Place, publisher, year, edition, pages
2011. Vol. 5, no 2, 351-361 p.
Keyword [en]
cellulose, chitin, functional diversity, species traits, T-RFLP
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-131083DOI: 10.1038/ismej.2010.119ISI: 000290020000018PubMedID: 20686511OAI: oai:DiVA.org:uu-131083DiVA: diva2:352721
Available from: 2010-09-22 Created: 2010-09-22 Last updated: 2017-11-30Bibliographically approved
In thesis
1. Bacterial Degradation and Use of Chitin in Aquatic Habitats
Open this publication in new window or tab >>Bacterial Degradation and Use of Chitin in Aquatic Habitats
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Chitin belongs to the most abundant biopolymers on earth where it has an important role as a structural element in crustaceans, insects, fungi and some phytoplankton. Missing evidence for long-term accumulation of chitin in nature implies fast turnover and as chitin is composed of aminosugar subunits it holds central roles in both carbon and nitrogen cycles. The aim of this thesis was to contribute to a better understanding of organic matter cycling by learning more about the diversity, function and ecology of bacteria that degrade chitin. A metagenome-enabled study of the spatial distribution of chitinolytic bacteria in aquatic ecosystems identified salinity as the major environmental factor for shaping their community composition. To address the role of alternative environmental variables controlling chitinolytic communities, a temporally resolved study was completed in a dimictic freshwater lake. Pronounced seasonal change in the indigenous chitinolytic community was observed and parallel measured environmental parameters pointed to the availability and crystalline form of chitin as significant controlling factors.  The different ecological niches occupied by microbes that utilize chitin for growth were studied in an experimental study. Single-cell quantification of chitinolytic cells and cells incorporating chitin hydrolysis products suggested that commensal use of chitin hydrolysis products without simultaneous chitinase activity could be an important ecological strategy in freshwater bacterioplankton communities. Members of the ubiquitous and often quantitatively dominant group of freshwater Actinobacteria Ac1 were identified as particularly active in this “cheater” lifestyle. Further experiments based on artificially created gradients in bacterial diversity demonstrated the importance of specific bacterial populations and community composition rather than overall community richness in controlling more specific functions such as chitin and cellulose degradation. To conclude, results of this thesis provide insight into the biogeography, niche-separation and species interactions of the functional community of chitin degraders and the influence of general bacterial diversity to the respective system functioning.

 

 

 

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 48 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 770
Keyword
Chitin, organic matter degradation, microbial ecology, functional guild
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-131128 (URN)978-91-554-7902-2 (ISBN)
Public defence
2010-11-05, Ekmansalen, Evolutionsbiologisk Centrum, Norbyv. 18 D, Uppsala, 10:00 (English)
Opponent
Supervisors
Note
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 700Available from: 2010-10-15 Created: 2010-09-23 Last updated: 2011-03-21Bibliographically approved
2. Diversity and Ecosystem Functioning: Redundancy and Resilience in Freshwater Bacterial Communities
Open this publication in new window or tab >>Diversity and Ecosystem Functioning: Redundancy and Resilience in Freshwater Bacterial Communities
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacteria are immensely diverse and hold key-positions in essentially all biogeochemical cycles. In freshwater ecosystems, bacteria degrade and mineralize organic compounds, linking the pool of dissolved organic matter to higher trophic levels. Aware of the global biodiversity loss, ecologists have started identifying the relationship of diversity and ecosystem functioning. Central to this is the question if species can functionally replace other species, hence being functionally redundant. Functional redundancy might allow communities to maintain functioning when diversity is lost. Due to their large numbers and great diversity, bacterial communities have been suspected to harbor large amounts of redundancy. The central aim of this thesis is to investigate the coupling of diversity and ecosystem functioning of bacterial communities and to understand how environmental perturbation affects this relationship. I manipulated the diversity of complex communities by a dilution technique, and measured the performance of bacterioplankton and biofilm-forming communities at different diversities. Reduction of bacterial diversity differently affected different functions, and that the presence or absence of certain species might be causing this pattern. However, for ecosystems to function, the interplay of multiple functions, i.e. multifunctionality, has to be sustained over long periods of time. In bacterial biofilm communities reduced diversity affected multifunctionality, as reflected by extracellular enzyme activities. A continuous cultivation system was used to address the importance of diversity for resistance and resilience upon environmental perturbation. The analysis of co-occurrence of bacterial taxa showed that the communities form a dense network before the perturbation and that these patterns are disturbed by the environmental perturbation. The final chapter of the thesis presents experimental evidence for the positive effects of temporal and spatial refuges for bacterial communities and the functions they provide. Overall, I found several indications for a lower amount of functional redundancy as previously assumed and it becomes apparent from this thesis that a multifunctional perspective and the consideration of environmental heterogeneity is pivotal.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 48 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 882
Keyword
biodiversity, ecosystem functioning, bacteria, fresh water, biofilms, multifunctionality, ecological networks, perturbation, fragility
National Category
Ecology Microbiology
Research subject
Biology with specialization in Limnology
Identifiers
urn:nbn:se:uu:diva-160780 (URN)978-91-554-8223-7 (ISBN)
Public defence
2011-12-16, Friessalen, Evolutionary Biology Centre (EBC), Norbyvägen 18, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2011-11-24 Created: 2011-10-31 Last updated: 2012-01-03

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Bertilsson, StefanLindström, Eva S.Langenheder, SilkeTranvik, Lars J.

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