Temperature impacts differentially on the methanogenic food web of cellulose‐supplemented peatland soil

Summary The impact of temperature on the largely unresolved intermediary ecosystem metabolism and associated unknown microbiota that link cellulose degradation and methane production in soils of a moderately acidic ( pH 4.5) fen was investigated. Supplemental [ 13 C ]cellulose stimulated the accumulation of propionate, acetate and carbon dioxide as well as initial methane production in anoxic peat soil slurries at 15° C and 5° C . Accumulation of organic acids at 15° C was twice as fast as that at 5° C . 16 S rRNA [ 13 C ]cellulose stable isotope probing identified novel unclassified Bacteria (79% identity to the next cultured relative F ibrobacter succinogenes ), unclassified B acteroidetes (89% identity to P rolixibacter bellariivorans ), P orphyromonadaceae , A cidobacteriaceae and R uminococcaceae as main anaerobic degraders of cellulose‐derived carbon at both 15° C and 5° C . H olophagaceae and S pirochaetaceae were more abundant at 15° C . C lostridiaceae dominated the degradation of cellulose‐derived carbon only at 5° C . M ethanosarcina was the dominant methanogenic taxa at both 15° C and 5° C . Relative abundance of M ethanocella increased at 15° C whereas that of M ethanoregula and M ethanosaeta increased at 5° C . T haumarchaeota closely related to N itrosotalea (presently not known to grow anaerobically) were abundant at 5° C but absent at 15° C indicating that N itrosotalea sp. might be capable of anaerobic growth at low temperatures in peat.