Degenhardt, D. | bioRxiv Science

bioRxiv2026

Biosensor monitoring of naphthenic acids remediation in mesocosms and constructed wetlands: a head-to-head comparison with orbitrap mass spectrometry.

Oil sands process-affected water (OSPW) contains complex mixtures of naphthenic acids (NA) that are the central targets for water treatment and reclamation. Here, we compared three whole-cell bacterial NA biosensors with Orbitrap mass spectrometry (MS) for quantifying NA remediation in greenhouse mesocosms and a pilot-scale constructed wetland. Solid-phase extracts from both systems were analyzed in parallel by Orbitrap MS and biosensor assays, enabling direct comparison of biosensor-derived NA estimates with MS-derived naphthenic acid fraction compounds (NAFC) concentrations. Across both treatment systems, biosensor outputs broadly tracked declines in NAFC measured by Orbitrap MS, and positive linear relationships were observed between methods. Biosensor 2 (3680-lux) and biosensor 3 (atuA-lux) showed, early rapid decreases in NA, whereas biosensor 1 (marR-lux) frequently remained elevated later in treatment. These differences are consistent with the distinct chemical response profiles of the biosensor panel and suggest that biosensor outputs reflect shifts in NA mixture composition as remediation proceeds. This interpretation is supported by the published Orbitrap analysis of the constructed wetland, which showed decreasing O2-NAFCs and increasing O3/O4-containing species, consistent with oxidative degradation. Together, these results support the use of NA-responsive biosensors as rapid and scalable complementary tools for tracking remediation trends, while Orbitrap MS remains the reference method for molecular-level characterization.

microbiology↗

bioRxiv2026

Synergistic plant-microbe interactions drive the remediation of naphthenic acid fractional compounds in a constructed wetland mesocosm

Constructed wetland treatment systems (CWTSs) are promising options for treating oil-sands process-affected water (OSPW), which contains toxic naphthenic acid fraction compounds (NAFCs). However, the molecular mechanisms underlying NAFCs attenuation by plants and root microbes remain poorly resolved. In our previous mesocosm study, common cattail (Typha latifolia) increased NAFCs removal by 2.5-fold relative to unplanted controls with no significant effect on plant growth. Here, using RNA from the same experimental system, we applied metatranscriptomics to 40 root samples collected over 60 days to examine plant and active-microbial responses to OSPW exposure. The active-root-associated-microbial community was dominated by Pseudomonadota, which showed a slight increase with exposure to OSPW. Burkholderiales were the most active family, though their relative activity decreased in OSPW systems, where Flavobacteriaceae (Bacteroidota) activity increased. Clear microbial-community shifts were driven by time and OSPW exposure. Although 18 previously proposed microbial NAFC-degradation genes were not differentially expressed, 42 other genes with potential roles in NAFC or related organic compound degradation showed differential expression in OSPW-filled mesocosms. This activity was dominated by specific oxidoreductases from Burkholderiales and Rhizobiales. Crucially, host plant actively responded to OSPW, robustly up-regulating genes encoding oxidoreductases, transporters, and glycosyltransferases, some of which are related to xenobiotic stress and detoxification. Taken together, these results show coordinated plant and microbial transcriptional responses in a system where NAFC removal had already been measured chemically. They help explain the response of OSPW-exposed mesocosms, but the observed patterns likely reflect the broader OSPW mixture rather than NAFCs alone.

ecology↗