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Uncoupling of chitinase activity and uptake of hydrolyses products in freshwater bacterioplankton
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för ekologi och genetik, Limnologi.
2011 (Engelska)Ingår i: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 56, nr 4, s. 1179-1188Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We investigated to what extent chitinolytic bacteria subsidize bacterial populations that do not produce chitinolytic enzymes but still use the products of chitin hydrolysis. Applying single-cell techniques to untreated and chitin-enriched lake water, we show that the number of planktonic cells taking up chitin hydrolysis products by far exceeds the number of cells expressing chitinases. Flavobacteria, Actinobacteria, and specifically members of the abundant and ubiquitous freshwater Ac1 cluster of the Actinobacteria, increased in abundance and were enriched in response to the chitin amendment. Flavobacteria were frequently observed in dense clusters on chitin particles, suggesting that they are actively involved in the hydrolysis and solubilization of chitin. In contrast, Actinobacteria were exclusively planktonic. We propose that planktonic Actinobacteria contain commensals specialized in the uptake of small hydrolysis products without expressing or possibly even possessing the machinery for chitin hydrolysis. More research is needed to assess the importance of such "cheater'' substrate acquisition strategies in the turnover and degradation of polymeric organic matter in aquatic ecosystems.

Ort, förlag, år, upplaga, sidor
2011. Vol. 56, nr 4, s. 1179-1188
Nationell ämneskategori
Biologiska vetenskaper
Identifikatorer
URN: urn:nbn:se:uu:diva-131094DOI: 10.4319/lo.2011.56.4.1179ISI: 000294603400001OAI: oai:DiVA.org:uu-131094DiVA, id: diva2:352761
Tillgänglig från: 2010-09-22 Skapad: 2010-09-22 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
Ingår i avhandling
1. Bacterial Degradation and Use of Chitin in Aquatic Habitats
Öppna denna publikation i ny flik eller fönster >>Bacterial Degradation and Use of Chitin in Aquatic Habitats
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

 

 

 

 

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2010. s. 48
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 770
Nyckelord
Chitin, organic matter degradation, microbial ecology, functional guild
Nationell ämneskategori
Biologiska vetenskaper
Identifikatorer
urn:nbn:se:uu:diva-131128 (URN)978-91-554-7902-2 (ISBN)
Disputation
2010-11-05, Ekmansalen, Evolutionsbiologisk Centrum, Norbyv. 18 D, Uppsala, 10:00 (Engelska)
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Anmärkning
Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 700Tillgänglig från: 2010-10-15 Skapad: 2010-09-23 Senast uppdaterad: 2011-03-21Bibliografiskt granskad

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