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Contribution of fungi and bacteria to the formation of dissolved organic carbon from decaying common reed (Phragmites australis)
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology. Federal Institute of Hydrology, Am Mainzer Tor 1, 56068 Koblenz, Germany.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 301, 12587 Berlin, Germany.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.ORCID iD: 0000-0003-3509-8266
2006 (English)In: Archiv für Hydrobiologie, ISSN 0003-9136, Vol. 166, no 1, 79-97 p.Article in journal (Refereed) Published
Abstract [en]

We examined release and subsequent utilization of DOC from leaves of common reed (Phragmites australis), a macrophyte which often dominates in shallow lakes and constitutes an important source of dissolved organic carbon (DOC). Leaves were incubated submersed in organic-free water for up to 63 days with natural and manipulated microbial communities. By this, we aimed to demonstrate differential effects of bacteria and fungi on the composition and amount of DOC originating from the leaves. DOC was analyzed by its total amount, spectral properties at wavelengths of 250-500 nm and its composition determined by size exclusion chromatography followed by organic carbon detection. Leaching of DOC was fast and the maximum DOC concentration was reached after 48 h. Mean molecule size increased during the first 14 days of incubation. Later on, humic-like substances accumulated, whereas low- and high-molecular-weight DOC were depleted. The formation of DOC from leaf detritus was strongly influenced by the composition of the microbial community present. Bacteria effectively removed low-molecular-weight DOC and accumulated high-molecular-weight DOC during a 7 day incubation. Leaf-degrading fungi promoted the accumulation of high amounts of intermediate-molecular-weight DOC, but were suppressed by the presence of bacteria. The presence of bacteria and/or fungi thus resulted in contrasting patterns of DOC composition, suggesting functional differences and strong interactions between those two major microbial groups during natural decomposition of leaves. The activity and interactions of both groups may therefore be significant for DOC composition in aquatic systems.

Place, publisher, year, edition, pages
2006. Vol. 166, no 1, 79-97 p.
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-92970DOI: 10.1127/0003-9136/2006/0166-0079ISI: 000238757500005OAI: oai:DiVA.org:uu-92970DiVA: diva2:166306
Available from: 2005-04-29 Created: 2005-04-29 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Interactions between Bacteria and Fungi on Aquatic Detritus – Causes and Consequences
Open this publication in new window or tab >>Interactions between Bacteria and Fungi on Aquatic Detritus – Causes and Consequences
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacteria and fungi dominate the decomposition of aquatic plants, a major process in the carbon and nutrient cycling in many aquatic systems. Although phylogenetically distant, bacteria and fungi often live in close proximity with each other. Since these microorganisms also have similar ecological functions, interactions have developed between them. This thesis explores the nature of such interactions, and the potential effects on key components of the decomposition process. The thesis includes a critical assessment of the ergosterol method for determination of fungal biomass, a survey of the environmental factors determining the distribution and taxa numbers of litter-decomposing bacteria and fungi in lakes, and a number of experiments on the interactions between bacteria and fungi. In all the experiments performed, fungi responded to bacterial presence through antagonism, although different fungal strains, bacterial communities and substrates were used. The antagonism seemed to be caused by interference competition for substrate. The fungal effect on bacteria was less consistent. Bacterial growth was suppressed, unaffected, or even enhanced by the presence of fungi. Fungi contributed more to extracellular enzyme production than bacteria, and bacteria were probably able to assimilate intermediate decomposition products formed through the activity of extracellular enzymes of fungal origin. Thus, the effect on bacteria from interacting with fungi was determined by the balance between competition and benefit from excreted enzymes. Bacteria and fungi also used different size fractions of the organic matter, according to their different enzymatic capacities. Hence, bacteria appeared to assimilate low-molecular-weight compounds, while high-molecular-weight compounds were utilized primarily by fungi.

In brief, the ecological interactions influenced the growth and hence also the biomass development of bacteria and fungi, which affected enzyme activity as well as utilization of dissolved organic matter. Therefore, I suggest that interactions between bacteria and fungi influence degradation of plant litter in aquatic systems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 42 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 46
Keyword
Ecology, bacteria, fungi, decomposition, antagonism, extracellular enzymes, competition, macrophytes, dissolved organic carbon (DOC), ergosterol, Ekologi
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-5771 (URN)91-554-6231-6 (ISBN)
Public defence
2005-05-20, Ekmansalen, Kärnhuset, EBC, Norbyv. 14, Uppsala, 10:00
Opponent
Supervisors
Available from: 2005-04-29 Created: 2005-04-29Bibliographically approved

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Tranvik, Lars J.

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