Degradation of Oxalate Containing Compounds by Soil Microbes
EMSL Project ID
4095
Abstract
Ectomycorrihizal mats are macroscopic structures occurring on the forest floor of the HJ Andrews Experimental Forest in the Oregon Cascade Mountains. They can cover up to 25% of the surface area of a forest stand (Cromack, 1979; Griffiths, 1996) and are of interest to researchers because of their possible contributions to carbon sequestration. Some of these mats weather rocks and small soil particles to gain nutrients by the secretion of oxalic acid. This weak acid creates a unique microhabitat populated by a host of specialized microbes, including oxalate-degrading bacteria. Oxalic acid decomposition occurs extremely rapidly in forest soils (Jones et al., 2001), and 50 to 85% of oxalate C added to O horizons can be mineralized to CO2 within 6 h (VanHees et al., 2002). Early work on these mat ecosystems found a high number of streptomyces (filamentous bacteria) (Knutson et al., 1980), although a wide variety of bacteria are capable of degrading these oxalate containing compounds. We propose to use TOF-SIMS, in order to gain insight about the transport of oxalate by the fungi and the identity of primary degraders. By adapting methods that have already been pioneered in our lab and others (Cliff et al., 2002; Orphan et al., 2001), we wish to analyze bacteria and fungi that have been grown on labeled substrate. We wish to use this technology to gain detailed images of mat forming hyphea and the organisms that may be living in close proximity, images not unlike those published a number of years ago (Graunstien and Cromack, 1977). The hyphal and oxalate crystal images produced by the TOF-SIMS system will provide more conclusive evidence that these oxalate containing compounds are indeed degraded in the mycorrhizosphere. Our ultimate goal is to use this technology to watch the incorporation of 13C glucose into hyphea strands, the release of these labeled carbon atoms as oxalate crystals into the soil, and the subsequent uptake of this oxalate by degrading bacteria. In preparation for this more complex system, we wish to use your facilities during the first week of September to gain spectra of 13C-and 12C-labeled pure culture specimens of oxalate-degrading streptomyces, as well as, spectra of precipitated oxalate crystals. We would also like to attempt to image a more complex slide using ions that have been successful in previous work: 12C, 13C, 24C2, 25C2. Gaining an image of oxalate incorporation will help us to better understand the spatial organization of this community, and will help us to determine if filamentous bacteria are in fact the primary degraders in this system.
Project Details
Project type
Exploratory Research
Start Date
2003-09-01
End Date
2004-09-16
Status
Closed
Released Data Link
Team
Principal Investigator