Occurrence and microbial tolerance of perfluorononanoic acid: A case study in Ontario municipal landfill

Perfluorononanoic acid (PFNA) is a long-chain per- and polyfluoroalkyl substance (PFAS) recognized for its environmental persistence and associated health concerns. This case study investigated indigenous microbial communities exposed to PFNA at a PFAS-impacted municipal landfill by isolating and characterizing PFNA-tolerant microorganisms from environmental samples. The presence of PFNA was confirmed using Fourier-transform infrared spectroscopy (FTIR), ultraviolet - visible (UV - Vis) spectrophotometry, and liquid chromatography - mass spectrometry (LC - MS). Five distinct microbial strains were isolated and incubated for 30 days in PFNA-enriched media (50 mg/L). All isolates maintained sustained growth and viability, as assessed through optical density measurements, dry biomass quantification, Gram staining, and morphological analysis. Molecular identification based on 16S rRNA and internal transcribed spacer (ITS) sequencing revealed bacterial genera including Bacillus, Stenotrophomonas, and Pseudomonas, as well as fungal genera such as Talaromyces and Paracremonium. The persistence of these bacterial and fungal isolates under continued PFNA exposure identifies them as candidates for further investigation in studies focused on PFNA transformation and degradation. This work provides site-specific insight into microbial tolerance to PFNA in landfill environments and establishes a foundation for future research on microbe - PFAS interactions.Implications: This study demonstrates that indigenous microbial communities in municipal landfill environments can tolerate prolonged exposure to perfluorononanoic acid (PFNA), a persistent per- and polyfluoroalkyl substance (PFAS). Identifying PFNA-tolerant bacterial and fungal genera is an essential step toward evaluating their potential use in future biodegradation and transformation studies. These findings are relevant to waste management professionals and environmental regulators because they improve understanding of PFNA persistence in landfill systems and help inform the design of biologically informed PFAS monitoring and remediation strategies.