Linking plastic degradation potential and resistance gene abundance in bacterioplankton community of the Sundarbans estuarine ecosystem.

Harnessing microbial capabilities offers a promising and sustainable approach to address the global challenge of plastic waste. However, the potential of mangrove microbiomes to degrade diverse plastic polymers remains largely unexplored. In this metagenomic-based study, surface water microbiomes were analysed from the Indian Sundarbans, part of the world's largest contiguous mangrove ecosystem, revealing 748.21 hits per billion nucleotides associated with plastic-degrading enzymes (PDEs) targeting 17 different polymer types. Of these, 72.9% corresponded to synthetic polymers and 27.1% to natural polymers. The highest number of hits (223) was associated with polyethylene glycol-degrading enzymes, representing 26.7% of the total PDEs hits. Taxonomic analysis revealed Deltaproteobacteria and Gammaproteobacteria as key degraders of diverse synthetic plastic polymers, with Deltaproteobacteria emerging as a previously unreported group. This suggests that surface sediments may serve as reservoirs for novel plastic-degrading microbes. Co-occurrence network analysis indicated possible emerging co-selection or complex associations between PDEs, antibiotic resistance genes (ARGs), and metal resistance genes (MRGs). Notably, zinc resistance genes and aminoglycoside-related ARGs showed more associations with PDEs. While the presence of PDEs offers a promising avenue for bioremediation, their application may be complicated by the concurrent rise of ARGs and MRGs within PDE-harbouring microbes. Thus, it highlights the need for careful assessment when employing microbes for plastic bioremediation.