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Interactions of bacteria and fungi on decomposing litter: Differential extracellular enzyme activities
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.ORCID iD: 0000-0003-3509-8266
2006 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 87, no 10, 2559-2569 p.Article in journal (Refereed) Published
Abstract [en]

Fungi and bacteria are key agents in plant litter decomposition in freshwater ecosystems. However, the specific roles of these two groups and their interactions during the decomposition process are unclear. We compared the growth and patterns of degradative enzymes expressed by communities of bacteria and fungi grown separately and in coexistence on Phragmites leaves. The two groups displayed both synergistic and antagonistic interactions. Bacteria grew better together with fungi than alone. In addition, there was a negative effect of bacteria on fungi, which appeared to be caused by suppression of fungal growth and biomass accrual rather than specifically affecting enzyme activity. Fungi growing alone had a high capacity for the decomposition of plant polymers such as lignin, cellulose, and hemicellulose. In contrast, enzyme activities were in general low when bacteria grew alone, and the activity of key enzymes in the degradation of lignin and cellulose (phenol oxidase and cellobiohydrolase) was undetectable in the bacteria-only treatment. Still, biomass-specific activities of most enzymes were higher in bacteria than in fungi. The low total activity and growth of bacteria in the absence of fungi in spite of apparent high enzymatic efficiency during the degradation of many substrates suggest that fungi provide the bacteria with resources that the bacteria were not able to acquire on their own, most probably intermediate decomposition products released by fungi that could be used by bacteria.

Place, publisher, year, edition, pages
2006. Vol. 87, no 10, 2559-2569 p.
Keyword [en]
antagonism/synergism, bacteria, extracellular enzyme activiy, freshwater-ecosystem litter degradation, fungi, leaf decomposition
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-92969DOI: 10.1890/0012-9658(2006)87[2559:IOBAFO]2.0.CO;2ISI: 000241557900016PubMedID: 17089664OAI: oai:DiVA.org:uu-92969DiVA: diva2:166305
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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