Impact of Pesticides and Oxygen on Cellulose Degradation by Prokaryotes in Aerated Agricultural Soils
O 1.6 in Funktion von Ökosystemen
15.04.2010, 10:30-10:45, H13
Cellulose is the most abundant biopolymer in agricultural soils. However, little is known about the diversity and function of soil prokaryotes that participate in its degradation. Cellulolytic and saccharolytic prokaryotes are present inside and on the surface of soil organomineral aggregates, where they are exposed to dynamic oxygen gradients. These redox gradients constitute a dynamic biogeochemical interface in soils. Pesticide residues in agriculture soils may affect the degradation and degraders of cellulose due to the toxic side-effects. The selective activation of cellulolytic and saccharolytic community under contrasting oxygen conditions was assessed by 16S rRNA 13C-based stable isotope probing (RNA SIP). Supplemented saccharides (cellulose, cellobiose, glucose) were converted to carbon dioxide in oxic, and to carbon dioxide, hydrogen and fermentation products, concomitant with the reduction of iron(III) in anoxic slurries. Species of 28 novel and 20 known family-level taxa were selectively activated under the different redox conditions and substrate supplements. Major phylotypes under oxic conditions were Intrasporangiaceae and Micrococcaceae (Actinobacteria), Bacteroidetes, Chloroflexi, and Planctomycetes. Kineosporiaceae (Actinobacteria), Bacteroidetes, and Clostridia degraded 13C substrates under anoxic conditions. Bentazon, 4-Nonylphenol, and MCPA inhibited cellulose and cellobiose degradation under both oxic and anoxic conditions. Cellulose degradation was strongly impacted under anoxic and less under oxic conditions. Cellobiose hydrolysis was less influenced than the subsequent degradation of glucose. Inhibitory effects were observed at in situ-relevant concentrations. Experiments are underway to resolve the specific effect of fluctuation redox potentials on single species/phylotypes with and without pesticides.
Export as iCal:
