Taxonomic and Metagenomic Survey of a Peat-Based Straw Degrading Biofertilizer

The mobilization of complex microbial communities from natural resources can be a valuable alternative to the use of single-species biofertilizers when it comes to the decomposition of plant residues. However, the functioning and interaction of microorganisms within these communities remain largely unexplored. Our task was to investigate the cellulose-degrading community using the biofertilizer BAGS (peat-based compost with straw) as an example and define its active component. For this, we monitored the succession of the biofertilizer's taxonomic composition during two consecutive rounds of its six-month composting process, varying in the applied mineral fertilization. The amount of added nitrogen significantly affected the performance of the biofertilizer, contributing to its high cellulolytic activity. Based on the network analysis, the biofertilizer's mature phase was determined, and its characteristic ASVs (amplicon sequence variants) were described. Metagenomic analysis of this phase revealed MAGs (metagenome-assembled genomes) corresponding to these ASVs, which contained genes for cellulose and aromatics degradation, as well as genes for nitrogen and sulfur pathways, including anaerobic nitrate reduction and thiosulfate oxidation. Thus, we propose that the cellulose-decomposing bacterial component of BAGS, associated with the mature phase, occupied different trophic niches, not limited to cellulose degradation, which should be considered when designing natural or artificial microbial systems for the decomposition of plant residues.