Divergent biofilm colonization on plastics in wastewater: Accelerated maturation on polyamide versus growth inhibition on biodegradable polymers

Microplastic (MP)-associated biofilms in wastewater treatment plants affect ecosystem integrity and treatment stability, yet their stage-specific developmental dynamics remain unresolved. This study characterized 30 d biofilm assembly dynamics on polyethylene (PE), polyamide (PA), and biodegradable poly(butylene adipate-co-terephthalate)/polylactic acid (BP) in simulated wastewater treatment systems. Integrated multi-parametric analyses revealed cyclic di-guanylate monophosphate (c-di-GMP) as a key biomarker of biofilm maturity, peaking at 15-22 d alongside maximal biomass and extracellular polymeric substances (EPS). Subsequent detachment was mediated by β-glucosidase and lysozyme, inducing autolysis. Stage-specific transitions included: Initial attachment (0-10 d); Microbial colonization (10-22 d); Maturation/Detachment (post-22 d). EPS-secreting and plastic-degrading taxa (Pseudomonas and Rhodotorula) facilitated initial attachment, followed by functional taxa mediating nitrogen transformation (Ochrobactrum, Aminobacter, and Cupriavidus) and potential biofilm-stabilizing fungi (Rozellomycota-gen-incertae-sedis). PA enhanced colonization via amide-driven nitrogen enrichment and elevated c-di-GMP levels, leading to robust biofilms with functional consortia (Zavarzinia, Sphingopyxis, and Rozellomycota-gen-incertae-sedis). Conversely, BP promoted initial bacterial recruitment (Pseudomonas and Enterobacter) but later inhibited sustained growth because of cytotoxic leachates and nutrient competition, causing biomass decline and fungal inhibition at 20 d. These findings elucidated plastisphere succession pathways, enabling more accurate assessment of their ecological impact and improved MP pollution management strategies in wastewater treatment.