Metagenomic Analysis of Polypropylene and Low-Density Polyethylene Plastispheres from an Intensive Agriculture Waste Landfill

Synthetic plastics are polymers that are largely produced worldwide, impacting ecosystems and human health. Microplastics are produced from fragmentation and degradation of larger plastics, as a consequence of environmental factors. Low-density polyethylene (LDPE) and polypropylene (PP) are plastic polymers acting as environmental hazards. Challenges in effective plastic waste management include sustainable and environmentally responsible approaches like microbial degradation. In this work, a shotgun metagenomic approach has been applied to analyze the response of the microorganisms living on plastic surfaces (plastispheres) of LDPE and PP to biodeterioration of these plastics (BioProject-NCBI, PRJNA1378224). Low-density polyethylene and polypropylene materials were collected from a waste landfill of intensive greenhouse agriculture. A further functional analysis supported putative roles of enzymes that could be involved in the initial steps of biodeterioration of LDPE and PP, including sarcosine oxidases; bromo- and chloro-peroxidases; cytochrome P450 and alkane monooxygenases; and multicopper oxidases. A CheckM analysis of genes that code for these oxidative enzymes revealed that they were mainly from the bacterial Phyllobacterium genus (Rhizobiaceae family) and, in less abundance, from the archaeon Methanoculleus genus (Methanoculleaceae family). This study supports putative roles of sarcosine oxidases and bromoperoxidases, and other relevant enzymes, in bacterial and archaeal LDPE and PP biodeterioration, highlighting the genomic potential of the microbiomes under study in biodeterioration of these synthetic plastics.