title: Microbial community dynamics associated with rhizosphere carbon flow.
abstract: Root-deposited photosynthate (rhizodeposition) is an important source of readily available carbon (C) for microbes in the vicinity of growing roots. Plant nutrient availability is controlled, to a large extent, by the cycling of this and other organic materials through the soil microbial community. Currently, our understanding of microbial community dynamics associated with rhizodeposition is limited. We used a (13)C pulse-chase labeling procedure to examine the incorporation of rhizodeposition into individual phospholipid fatty acids (PLFAs) in the bulk and rhizosphere soils of greenhouse-grown annual ryegrass (Lolium multiflorum Lam. var. Gulf). Labeling took place during a growth stage in transition between active root growth and rapid shoot growth on one set of plants (labeling period 1) and 9 days later during the rapid shoot growth stage on another set of plants (labeling period 2). Temporal differences in microbial community composition were more apparent than spatial differences, with a greater relative abundance of PLFAs from gram-positive organisms (i15:0 and a15:0) in the second labeling period. Although more abundant, gram-positive organisms appeared to be less actively utilizing rhizodeposited C in labeling period 2 than in labeling period 1. Gram-negative bacteria associated with the 16:1omega5 PLFA were more active in utilizing (13)C-labeled rhizodeposits in the second labeling period than in the first labeling period. In both labeling periods, however, the fungal PLFA 18:2omega6,9 was the most highly labeled. These results demonstrate the effectiveness of using (13)C labeling and PLFA analysis to examine the microbial dynamics associated with rhizosphere C cycling by focusing on the members actively involved.
authors: Departments of Crop and Soil Science. Microbiology, Oregon State University, Corvallis, Oregon 97331, USA.
authors: Jessica L
authors: JL
authors: Butler
authors: Mark A
authors: MA
authors: Williams
authors: Peter J
authors: PJ
authors: Bottomley
authors: David D
authors: DD
authors: Myrold
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes / Q000378:metabolism; D017753:Ecosystem; D005227:Fatty Acids / Q000032:analysis; D006090:Gram-Negative Bacteria / Q000145:classification / Q000254:growth & development; D006094:Gram-Positive Bacteria / Q000145:classification / Q000254:growth & development; D008129:Lolium / Q000254:growth & development / Q000382:microbiology*; D038821:Mycorrhizae; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology*; D012988:Soil Microbiology
chemical_list: D002247:Carbon Isotopes; D005227:Fatty Acids; D002244:Carbon