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Plastisphere-isolated Stutzerimonas balearica SP-H sustains stable sulfur-autotrophic denitrification under microplastic stress
Summary
Scientists found that a bacteria strain living naturally on plastic waste in wetlands can keep breaking down harmful nitrogen pollution even when surrounded by microplastics—while a "normal" bacteria strain struggles and produces more nitrous oxide (a greenhouse gas) and pollution byproducts when exposed to the same plastic bits. This matters because it suggests we could use these plastic-tolerant bacteria to help wastewater treatment systems keep working properly despite the growing microplastic pollution problem, potentially protecting water quality that affects human health.
Microplastic (MP) accumulation in constructed wetlands potentially threatens sulfur-autotrophic denitrification under low C/N conditions, yet the resilience of plastisphere-derived denitrifiers remains poorly understood. Here, we isolated and compared two denitrifying strains, a plastisphere isolate, Stutzerimonas balearica SP-H, and a conventional wetland isolate, Castellaniella denitrificans S0-H, under polyamide (PA) and polyethylene (PE) MP exposure. MPs severely impaired strain S0-H, causing nitrate removal inhibition (50.40–74.42%), nitrite accumulation (93.54–95.79%), elevated N 2 O production (57.24–94.32%), and reduced sulfate generation (38.94–66.95%). In contrast, strain SP-H maintained efficient nitrate depletion and stable sulfur oxidation under MP stress. Mechanistically, strain SP-H's superior tolerance involved a coordinated multi-layered defense: higher activities of Nar, Nir, and Sox, upregulated c-di-GMP, enhanced polysaccharide-rich extracellular polymeric substances (EPS) production, and preserved ATP levels. Collectively, habitat origin may determine MP resistance, and plastisphere-isolated strains like SP-H represent promising bioaugmentation agents to stabilize sulfur-based autotrophic denitrification in MP-impacted wastewater systems.