Upregulation of organic N genes under soil warming

Global warming increases soil temperatures and promotes faster growth and turnover of soil microbial communities. Previous studies have shown that long-term warming depleted soils of easily accessible substrates for microbial growth, resulting in a lower microbial biomass, but at sustained higher growth and turnover rates. Since microbial cell walls contain a high proportion of organic nitrogen, a higher turnover rate of microbes should also be reflected in an accelerated organic nitrogen cycling in soil. We investigated the microbial cycling of organic nitrogen under warming and ambient soils using metatranscriptomics and metagenomics, and focused on the relative transcription levels of genes encoding proteins involved in the extracellular depolymerization of nitrogen-containing polymers, such as proteins, nucleic acids, chitin and peptidoglycans. Our findings show microbial communities upregulated their gene expression to target alternative organic nitrogen substrates under warming. In particular, we found higher transcription levels of genes coding for enzymes degrading protein, peptidoglycan and microbial cell walls under warming. This highlights the importance of microbial necromass for organic N cycling in soils in general, and specifically in warmed soils.Sequencing was performed at the Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna under the project ID JMF-1901-4.