Degradation of C-13-U-glucose in Sphagnum majus litter: Responses to redox, pH, and temperature

We studied the utilization of C-13-U-glucose by the microbial community in shallow Sphagnum majus (Russ.) C. Jens. ssp. norvegicum Flatb. litter and i ts regulation by pH, temperature, and redox conditions. The transformation of C-13-glucose was monitored by solution- and solid-state C-13-nuclear mag netic resonance (MMR) spectroscopy. The aerobic microbial community used th e glucose C for respiration and, to a lesser degree, for storage as mannito l, triglycerides, and polysaccharides. Under both aerobic and anaerobic con ditions, the allocation of glucose C for storage was greater at pH 6.8 than at 4.3; however, the amount of C used for building new biomass was the sam e at both pH settings. At 15 degrees C, 15 to 18% of the utilized C under a erobic conditions was found in new microbial biomass: less than the previou sly reported values of 40 to 72%. This indicates that peat soils may promot e significantly different microbial growth patterns from other minerogenic and moor humus soils. The production of mannitol and triglycerides suggests that fungi dominated the microbial community and utilized the glucose unde r aerobic conditions. Using a combination of solid and liquid NMR technique s we were able, for the first time, to follow the anaerobic pathways of glu cose degradation in a natural soil sample. The anaerobic microbial communit y produced mainly volatile fatty acids (VFA), ethanol, and CO2 from the add ed glucose, and only minor amounts were converted to methane, storage C, an d new microbial biomass. Nuclear magnetic resonance spectroscopy allows non destructive assays of metabolic events and, therefore, was shown to be an e xcellent tool for studying the microbial utilization of C-13-glucose in pea t.