Abstract
Microbial activity in soil is generally assumed to be limited by carbon availability. The soil closest to roots, the rhizosphere, is therefore a zone of high microbial activity due to carbon containing substances released by the root. In this work short-term effects in the rhizosphere have been the subject of investigation. I have shown that the thymidine and leucine incorporation techniques are well suited to the study of the effect of roots on rhizosphere bacterial activity. Bacterial activity in the rhizosphere was found to be 2-4 times higher than in the bulk soil. The turnover time found for rhizosphere bacteria was in the same range as those reported earlier. Bacterial activity in the rhizosphere increased with time, both when barley seedlings were studied at different ages and when samples were taken along the root. The effect of nitrogen addition on the activity of rhizosphere bacteria varied with the nitrogen source added, and were related to the pH induced in the rhizosphere. Toxic substances inhibiting bacterial activity were released from leek roots during the extraction of bacteria due to root injury during the sampling procedure. The composition of the microbial community in the rhizosphere was investigated using three different techniques: direct soil-PLFA, cfu-PLFA and CLPP (Biolog). All three methods were found suitable for rhizosphere studies. Different plant species were found to influence the rhizosphere bacteria differently, concerning both activity and community composition. Arbuscular mycorrhizal (AM) colonisation also influences rhizosphere bacteria differently depending on plant species. Plant species had a greater effect on the bacterial community in the rhizosphere than AM colonisation. This work demonstrates that the direct measurement technique of thymidine and leucine incorporation has the potential to become a useful tool in studies of bacterial activity in the rhizosphere.
| Original language | English |
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| Qualification | Doctor |
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| Award date | 2003 Mar 7 |
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| ISBN (Print) | 91-7105-187-2 |
| Publication status | Published - 2003 |
Bibliographical note
Defence detailsDate: 2003-03-07
Time: 10:15
Place: N/A
External reviewer(s)
Name: Christensen, Sören
Title: [unknown]
Affiliation: [unknown]
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Article: I Söderberg, K. H., Bååth, E. (1998) Bacterial activity along a young barley root measured by the thymidine and leucine incorporation techniques. Soil Biology and Biochemistry 30: 1259-1268II Bååth, E., Pettersson, M. and Söderberg, K. H. (2001) Adaptation of a rapid and economical microcentrifugation method to measure thymidine and leucine incorporation by soil bacteria. Soil Biology and Biochemistry 33: 1571-1574.III Söderberg, K. H. and Bååth, E. (2003) The influence of nitrogen fertilisation on bacterial activity in the rhizosphere of barley. SubmittedIV Söderberg, K. H., Olsson, P. A. and Bååth, E. (2002) Structure and activity of the bacterial community in the rhizosphere of different plant species and the effect of arbuscular mycorrhizal colonisation. FEMS Microbiology Ecology 40: 223-231.V Söderberg, K. H. and Bååth, E. (2003) Bacterial activity in the rhizosphere of leek roots influenced by root injury during extraction of bacteria. ManuscriptVI Söderberg, K. H., Probanza, A., Jumpponen, A. and Bååth, E. (2003) The microbial community in the rhizosphere determined with community-level physiological profiles (CLPP) and direct soil and cfu-PLFA techniques. Manuscript
Subject classification (UKÄ)
- Ecology (including Biodiversity Conservation)
Free keywords
- CLPP
- Microbiology
- bacteriology
- virology
- mycology
- Mikrobiologi
- bakteriologi
- virologi
- mykologi
- Biolog
- PLFA
- mycorrhizal status
- nitrogen addition
- along roots
- plant species
- root age
- thymidine and leucine incorporation
- bacterial composition
- Rhizosphere
- bacterial activity