Preliminary investigation of microorganisms potentially involved in microplastics degradation using an integrated metagenomic and biochemical approach.

Plastic pollution is becoming an emerging environmental issue due to inappropriate disposal at the end of the materials life cycle. When plastics are released, they undergo physical and chemical corrosion, leading to the formation of small particles, commonly referred to as microplastics. In this study, a microbial community derived from the leachate of a bioreactor containing a mixture of soil and plastic collected during a landfill mining process underwent an enrichment protocol in order to select the microbial species specifically involved in plastic degradation. The procedure was set up and tested on polyethylene, polyvinyl chloride, and polyethylene terephthalate, both in anaerobic and aerobic conditions. The evolution of the microbiome has been monitored using a combined approach based on microscopy, marker-gene amplicon sequencing, genome-centric metagenomics, degradation assays, and GC-MS analyses. This procedure permitted us to deeply investigate the metabolic pathways potentially involved in plastic degradation and to depict the route for microplastics metabolization from the enriched microbial community. Six enzymes, among the ones already identified, were found in our samples (alkane 1-monooxygenase, cutinase, feruloyl esterase, triacylglycerol lipase, medium-chain acyl-CoA dehydrogenase, and protocatechuate 4,5-dioxygenase) and new enzymes, addressed as MHETases most probably for the presence of the catalytic triad (His-Asp-Ser), were detected. Among the enzymes involved in plastics degradation, alkane 1-monooxygenase was found in high copy number (between ten and 62 copies) in the metagenomes that resulted most abundant in the microbiome enriched with polyethylene, while protocatechuate 4,5-dioxygenase was found between one and eight copies in the most abundant metagenomes of the microbial culture enriched with polyethylene terephthalate. Degradation assays, performed using both bacterial lysates and supernatants, revealed interesting results on polyethylene terephthalate degradation. Moreover, this study demonstrates to what extent different types of microplastics can affect the microbial community composition. The results obtained significantly increase the knowledge of the plastic degradation process.

Large-scale sequencing and comparative analysis of oenological Saccharomyces cerevisiae strains supported by nanopore refinement of key genomes.

Saccharomyces cerevisiae has long been part of human activities related to the production of food and wine. The industrial demand for fermented beverages with well-defined and stable characteristics boosted the isolation and selection of strains conferring a distinctive aroma profile to the final product. To uncover variants characterizing oenological strains, the sequencing of 65 new S. cerevisiae isolates, and the comparison with other 503 publicly available genomes were performed. A hybrid approach based on short Illumina and long Oxford Nanopore reads allowed the in-depth investigation of eleven genomes and the identification of putative laterally transferred regions and structural variants. A comparative analysis between clusters of strains belonging to different datasets allowed the identification of novel relevant genetic features including single nucleotide polymorphisms, insertions and structural variants. Detection of oenological single nucleotide variants shed light on the existence of different levels of modulation for the mevalonate pathway relevant for the biosynthesis of aromatic compounds.