title: Fungal and bacterial utilization of organic substrates depends on substrate complexity and N availability.
abstract: There is growing evidence of a direct relationship between microbial community composition and function, which implies that distinct microbial communities vary in their functional properties. The aim of this study was to determine whether differences in initial substrate utilization between distinct microbial communities are due to the activities of certain microbial groups. We performed a short-term experiment with beech forest soils characterized by three different microbial communities (winter and summer community, and a community from a tree-girdling plot). We incubated these soils with different (13) C-labelled substrates with or without inorganic N addition and analyzed microbial substrate utilization by (13) C-phospholipid fatty acid (PLFA) analysis. Our results revealed that the fate of labile C (glucose) was similar in the three microbial communities, despite differences in absolute substrate incorporation between the summer and winter community. The active microbial community involved in degradation of complex C substrates (cellulose, plant cell walls), however, differed between girdling and control plots and was strongly affected by inorganic N addition. Enhanced N availability strongly increased fungal degradation of cellulose and plant cell walls. Our results indicate that fungi, at least in the presence of a high N supply, are the main decomposers of polymeric C substrates.
authors.affiliation: Department of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria.
authors.forename: Marianne
authors.initials: M
authors.lastname: Koranda
authors.forename: Christina
authors.initials: C
authors.lastname: Kaiser
authors.forename: Lucia
authors.initials: L
authors.lastname: Fuchslueger
authors.forename: Barbara
authors.initials: B
authors.lastname: Kitzler
authors.forename: Angela
authors.initials: A
authors.lastname: Sessitsch
authors.forename: Sophie
authors.initials: S
authors.lastname: Zechmeister-Boltenstern
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D002244:Carbon / Q000032:analysis / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism; D005658:Fungi / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D014197:Trees / Q000378:metabolism / Q000382:microbiology
chemical_list: D012987:Soil; D002244:Carbon; D002482:Cellulose; D009584:Nitrogen
keywords: 13C-phospholipid fatty acid analysis; microbial community; respiration; substrate utilization