The distinct plastisphere microbiome in the terrestrial-marine ecotone is a reservoir for putative degraders of petroleum-based polymers.

Research into plastic-degrading bacteria and fungi is important for understanding how microorganisms can be used to address the problem of plastic pollution and for developing new approaches to sustainable waste management and bioplastic production. In the present study, we isolated 55 bacterial and 184 fungal strains degrading polycaprolactone (PCL) in plastic waste samples from Dafeng coastal salt marshes, Jiangsu, China. Of these, Jonesia and Streptomyces bacteria also showed potential to degrade other types of petroleum-based polymers. The metabarcoding results proved the existence of plastisphere as a distinct ecological niche regardless of the plastic types where 27 bacterial and 29 fungal amplicon sequence variants (ASVs) were found to be significantly (p < 0.05) enriched, including some belonging to Alternaria (Ascomycota, Fungi) and Pseudomonas (Gammaproteobacteria, Bacteria) that were also mined out by the method of cultivation. Further assembly analyses demonstrated the importance of deterministic processes especially the environmental filtering effect of carbon content and pH on bacteria as well as the carbon and cation content on fungi in shaping the plastisphere communities in this ecosystem. Thus, the unique microbiome of the plastisphere in the terrestrial-marine ecotone is enriched with microorganisms that are potentially capable of utilizing petroleum-based polymers, making it a valuable resource for screening plastic biodegraders.

Characterization of an Exceptional Fungal Mutant Enables the Discovery of the Specific Regulator of a Silent PKS-NRPS Hybrid Biosynthetic Pathway.

Filamentous fungi produce a great variety of bioactive secondary metabolites essential for their biotic interactions. Here, we characterized an exceptional Trichoderma mutant overproducing harzianic acids (HAs) with exclusively highly antifungal activity against numerous fungi from different ecological groups. Interestingly, two transcription factors (TFs) were identified in this HA biosynthetic gene cluster (hac BGC), with HacI regulating the biosynthetic genes and HacF being likely responsible for the product transportation essential for the self-detoxification of the fungus from the produced HAs. Evolutionary analysis suggested that the sparse distribution of hac BGC in many environmental opportunistic fungi including several species from Trichoderma, Penicillium, and Aspergillus could result from lateral gene transfers and pervasive gene losses in different lineages of Pezizomycotina. Taken together, we propose that the production of HAs by fungi is to inhibit the growth of the surrounding partners to secure an exclusive position in a competitive community.