Enterobacteriaceae facilitate the anaerobic degradation of glucose by a forest soil

Anoxic micro zones that occur in soil aggregates of oxic soils may be temporarily extended after rainfall and thus facilitate the anaerobic degradation of organic compounds in soils. The microbial degradation of glucose by anoxic slurries of a forest soil yielded acetate, CO2, H2, succinate, and ethanol, products indicative of mixed acid fermentation. Prokaryotes involved in this process were identified by time-resolved 16S rRNA gene-targeted stable isotope probing with [13C-U]-glucose. All labeled phylotypes from the 13C-enriched 16S rRNA gene were most closely related to Rahnella and Ewingella, enterobacterial genera known to catalyze mixed acid fermentation. These results indicate that facultative aerobes, in particular Enterobacteriaceae, (1) can outcompete obligate anaerobes when conditions become anoxic in forest soils and (2) may be involved in the initial decomposition of monosaccharides in anoxic micro zones of aerated forest soils.