Recent advances in meta-omics and particularly metatranscriptomic approaches have enabled detailed studies of the structureand function of microbial communities in many ecosystems. Molecular analyses of peat soils, ecosystems important to the globalcarbon balance, are still challenging due to the presence of coextracted substances that inhibit enzymes used in downstream applications.We sampled layers at different depths from two high-Arctic peat soils in Svalbard for metatranscriptome preparation.Here we show that enzyme inhibition in the preparation of metatranscriptomic libraries can be circumvented by linear amplificationof diluted template RNA. A comparative analysis of mRNA-enriched and nonenriched metatranscriptomes showed thatmRNA enrichment resulted in a 2-fold increase in the relative abundance of mRNA but biased the relative distribution of mRNA.The relative abundance of transcripts for cellulose degradation decreased with depth, while the transcripts for hemicellulosedebranching increased, indicating that the polysaccharide composition of the peat was different in the deeper and older layers.Taxonomic annotation revealed that Actinobacteria and Bacteroidetes were the dominating polysaccharide decomposers. Therelative abundances of 16S rRNA and mRNA transcripts of methanogenic Archaea increased substantially with depth. Acetoclasticmethanogenesis was the dominating pathway, followed by methanogenesis from formate. The relative abundances of 16SrRNA and mRNA assigned to the methanotrophic Methylococcaceae, primarily Methylobacter, increased with depth. In conclusion,linear amplification of total RNA and deep sequencing constituted the preferred method for metatranscriptomic preparationto enable high-resolution functional and taxonomic analyses of the active microbiota in Arctic peat soil.
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