HR: 0800h
AN: B31A-0967    [Abstracts]
TI: Substrate Diffusion Heterogeneity Controls Bacterial Competition and Coexistence
AU: * Dechesne, A
EM: ard@er.dtu.dk
AF: Institute of Environment & Resources Technical University of Denmark, Bygningstorvet, Building 115, Kgs. Lyngby, DK-2800 Denmark
AU: * Dechesne, A
EM: ard@er.dtu.dk
AF: Department of Civil and Environmental Engineering University of Connecticut, 261 Glenbrook Road, Unit 2037, Storrs, CT 06269 United States
AU: Or, D
EM: dani@engr.uconn.edu
AF: Department of Civil and Environmental Engineering University of Connecticut, 261 Glenbrook Road, Unit 2037, Storrs, CT 06269 United States
AU: Smets, B F
EM: bfs@er.dtu.dk
AF: Institute of Environment & Resources Technical University of Denmark, Bygningstorvet, Building 115, Kgs. Lyngby, DK-2800 Denmark
AB: Diffusion has long been recognized as a key process affecting bacterial physiological functions ranging from nutrient uptake to removal of metabolic waste products. In the vadose zone, significant convective flows are limited and bacteria rely primarily on diffusion for nutrient supply. Even under relatively "wet" conditions (e.g. matric potentials -20 J/kg), soil water is fragmented and exists as thin liquid films or held in crevices imposing constraints on substrate diffusion. Our objective was to investigate the role of diffusion on soil microbial diversity, by focusing on one of the processes that shapes the structure of bacterial communities: competitive interactions. We used a simplified setup, in which the substrate (citrate) fluxes were controlled by different agar gels thicknesses and spatially heterogeneous diffusive pathways were created by an impermeable film with prescribed hole sizes and patterns. Our competition experiments involved two soil bacteria: Burkholderia xenovorans LB400 and Pseudomonas putida KT2440, which were tagged with different constitutive fluorescent markers, allowing for their on line microscopic detection. The growth parameters on citrate of these strains were thoroughly assessed. B. xenovorans LB400 is the weaker competitor. As a result, this strain was outcompeted by KT2440 under high substrate diffusivity and homogeneous conditions. Conversely, the disadvantage of the weakest competitor was not so marked under low substrate diffusivity condition. These results suggest that dry conditions in soil would provide conditions allowing the sustaining of weak bacterial competitors, resulting in the maintenance of high bacterial diversity.
DE: 0410 Biodiversity
DE: 0448 Geomicrobiology
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 1875 Vadose zone
SC: Biogeosciences [B]
MN: Fall Meeting 2005