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Delineating degradation of polyethylene microplastics by mangrove-derived microbes: Enzymatic pathways and intermediate identification
Summary
Two bacterial strains isolated from plastic-coated biofilm in a Thai mangrove — Lysobacter sp. and Nitratireductor kimnyeongensis — degraded 35% and 23% of polyethylene microplastics by weight within 30 days, using distinct metabolic pathways confirmed by genomic analysis. Finding effective plastic-degrading microbes in mangrove environments is significant because mangroves are both major accumulation zones for coastal plastic pollution and highly biodiverse ecosystems where natural microbial solutions could potentially be harnessed for in-situ cleanup.
The accumulation of polyethylene microplastics (PE-MPs) in marine and coastal environments, particularly mangrove ecosystems, poses significant environmental challenges. To address this, we investigated the bioremediation potential of two bacterial strains, Lysobacter sp. (MAS-1) and Nitratireductor kimnyeongensis (MAS-2), isolated from biofilm-coated PE-film in a Thailand mangrove area. Microbial community analysis revealed a shift toward Proteobacteria (47-92 %) and Actinomycetota (5-41 %) in PE-MP-enriched consortia, indicating niche specialization. Both strains exhibited significant degradation, with MAS-1 achieving 35.4 ± 1.2 % and MAS-2 achieving 23.04 ± 0.8 % weight loss of PE-MPs within 30-days. Biofilm assays confirmed substantial microbial adhesion on PE-MPs, and SEM imaging revealed surface pitting and cracking, indicative of microbial colonization and polymer breakdown. While FT-IR analyses showed oxidative modifications including carbonyl (CO), hydroxyl (-OH), and ether (C-O) groups, enhancing PE surface hydrophilicity. LC-MS/MS identified organic acids and nitrogen- and sulfur-rich compounds in a liquid medium, with in silico BioTransformer 3.0 analysis predicting strain-specific pathways like sulfur oxidation for MAS-1 and dehalogenation of MAS-2. These findings establish the bioremediation potential of mangrove-derived microbes and highlight the strains' distinct metabolic roles in PE-MP degradation.