ena-STUDY-UNIVERSITY OF BAYREUTH-18-07-2016-14:37:29:626-1034
Oxygen shapes trophic interactions of a chitin-degrading soil microbiome
Chitin is an abundant component in soil and constitutes therefore a major precursor of atmospheric CO2, which is released by microbial degradation. The dependence on oxygen of trophic interactions in chitin-degrading soil microbiomes is largely unknown. [13Cu]chitin-based RNA and protein stable isotope probing was conducted to resolve these interactions in an agricultural soil in the presence and absence of oxygen. Beta- and Gammaproteobacteria  and Bacteroidetes were the first to indicate that they transform chitin since 13C incorporation was detected after 3 days in the presence of oxygen. Subsequently, Planctomycetes and Verrucomicrobia assimilated 13C, suggesting that they either were degraders of chitin or functioned as 'satellite microbes,' metabolizing the excess chitin hydrolysis products. Predatory members of Deltaproteobacteria incorporated 13C after 10 days and the abundance of non-labeled predatory microeukaryotes also increased. Under anoxic conditions, butyric and propionic acid fermentation occurred along with iron respiration. Firmicutes and Bacteroidetes were predominantly labeled, suggesting that both bacterial groups contributed to chitin degradation and provided substrates for iron reducers. Active soil microorganisms and their interactions substantially changed under different oxygen regimes. Ultimately, our study provides an observation-based interaction model of microbial chitin mineralization in soils.
Chitin is an abundant component in soil and constitutes therefore a major precursor of atmospheric CO2, which is released by microbial degradation. The dependence on oxygen of trophic interactions in chitin-degrading soil microbiomes is largely unknown. [13Cu]chitin-based RNA and protein stable isotope probing was conducted to resolve these interactions in an agricultural soil in the presence and absence of oxygen. Beta- and Gammaproteobacteria  and Bacteroidetes were the first to indicate that they transform chitin since 13C incorporation was detected after 3 days in the presence of oxygen. Subsequently, Planctomycetes and Verrucomicrobia assimilated 13C, suggesting that they either were degraders of chitin or functioned as 'satellite microbes,' metabolizing the excess chitin hydrolysis products. Predatory members of Deltaproteobacteria incorporated 13C after 10 days and the abundance of non-labeled predatory microeukaryotes also increased. Under anoxic conditions, butyric and propionic acid fermentation occurred along with iron respiration. Firmicutes and Bacteroidetes were predominantly labeled, suggesting that both bacterial groups contributed to chitin degradation and provided substrates for iron reducers. Active soil microorganisms and their interactions substantially changed under different oxygen regimes. Ultimately, our study provides an observation-based interaction model of microbial chitin mineralization in soils.