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Applied and Environmental Microbiology, June 2009, p. 3611-3620, Vol. 75, No. 11
0099-2240/09/$08.00+0     doi:10.1128/AEM.02865-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Differential Utilization of Carbon Substrates by Bacteria and Fungi in Tundra Soil{triangledown}

Riikka Rinnan1,2* and Erland Bååth1

Department of Microbial Ecology, Lund University, Ecology Building, SE-22362 Lund, Sweden,1 Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark2

Received 17 December 2008/ Accepted 3 April 2009

Little is known about the contribution of bacteria and fungi to decomposition of different carbon compounds in arctic soils, which are an important carbon store and possibly vulnerable to climate warming. Soil samples from a subarctic tundra heath were incubated with 13C-labeled glucose, acetic acid, glycine, starch, and vanillin, and the incorporation of 13C into different phospholipid fatty acids (PLFA; indicative of growth) and neutral lipid fatty acids (NLFA; indicative of fungal storage) was measured after 1 and 7 days. The use of 13C-labeled substrates allowed the addition of substrates at concentrations low enough not to affect the total amount of PLFA. The label of glucose and acetic acid was rapidly incorporated into the PLFA in a pattern largely corresponding to the fatty acid concentration profile, while glycine and especially starch were mainly taken up by bacteria and not fungi, showing that different groups of the microbial community were responsible for substrate utilization. The 13C-incorporation from the complex substrates (starch and vanillin) increased over time. There was significant allocation of 13C into the fungal NLFA, except for starch. For glucose, acetic acid, and glycine, the allocation decreased over time, indicating use of the storage products, whereas for vanillin incorporation into fungal NLFA increased during the incubation. In addition to providing information on functioning of the microbial communities in an arctic soil, our study showed that the combination of PLFA and NLFA analyses yields additional information on the dynamics of substrate degradation.

* Corresponding author. Mailing address: Terrestrial Ecology Section, Department of Biology, University of Copenhagen, Øster Farimagsgade 2D, DK-1353 Copenhagen K, Denmark. Phone: 45 35 32 22 44. Fax: 45 35 32 23 21. E-mail: riikkar{at}bio.ku.dk

{triangledown} Published ahead of print on 10 April 2009.

Applied and Environmental Microbiology, June 2009, p. 3611-3620, Vol. 75, No. 11
0099-2240/09/$08.00+0     doi:10.1128/AEM.02865-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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