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Pronounced seasonal dynamics of freshwater chitinase genes and chitin processing
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
Département de Biologie, Québec-Océan and Institut de biologie integrative et des systèmes, Université Laval.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular Evolution.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Population and Conservation Biology.
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2012 (English)In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 14, no 9, 2467-2479 p.Article in journal (Refereed) Published
Abstract [en]

Seasonal variation in activity of enzymes involved in polymer degradation, including chitinases, has been observed previously in freshwater environments. However, it is not known whether the seasonal dynamics are due to shifts in the activity of bacteria already present, or shifts in community structure towards emergence or disappearance of chitinolytic organisms. We traced seasonal shifts in the chitinase gene assemblage in a temperate lake and linked these communities to variation in chitinase activity. Chitinase genes from 20 samples collected over a full yearly cycle were characterized by pyrosequencing. Pronounced temporal shifts in composition of the chitinase gene pool (beta diversity) occurred along with distinct shifts in richness (alpha diversity) as well as chitin processing. Changes in the chitinase gene pool correlated mainly with temperature, abundance of crustacean zooplankton and phytoplankton blooms. Also changes in the physical structure of the lake, e.g. stratification and mixing were associated with changes in the chitinolytic community, while differences were minor between surface and suboxic hypolimnetic water. The lake characteristics influencing the chitinolytic community are all linked to changes in organic particles and we suggest that seasonal changes in particle quality and availability foster microbial communities adapted to efficiently degrade them.

Place, publisher, year, edition, pages
2012. Vol. 14, no 9, 2467-2479 p.
Keyword [en]
chitinase genes, lake, temporal dynamics, seasonality, pyrosequencing
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-131091DOI: 10.1111/j.1462-2920.2012.02764.xISI: 000308300600018OAI: oai:DiVA.org:uu-131091DiVA: diva2:352757
Available from: 2010-09-22 Created: 2010-09-22 Last updated: 2012-10-08Bibliographically 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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 770
Chitin, organic matter degradation, microbial ecology, functional guild
National Category
Biological Sciences
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)
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

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Ettema, Thijs J. G.Östman, ÖrjanTranvik, Lars J.Bertilsson, Stefan
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