Fanglian Lu

Nonylphenol (NP), a typical emerging pollutant, is widely detected in water bodies, yet its hepatotoxic mechanisms and mitigation strategies remain underexplored. This study evaluated the protective effects of a mixed probiotic (Lactobacillus acidophilus and Bacillus subtilis) against NP-induced hepatotoxicity in Silurus meridionalis by integrating transcriptomic and metabolomic analyses, with validation by RT-qPCR and ELISA. The results showed that NP exposure disrupted the arachidonic acid (AA) pathway (activating pro-inflammatory COX and LOX pathways while the suppressing anti-inflammatory CYP450 branch), promoted ferroptosis via iron dyshomeostasis and oxidative damage, and impaired triglyceride (TG) synthesis. Probiotic pretreatment reversed these toxic effects by modulating AA metabolism, suppressing COX (ptgs2a↓ → PGE₂↓) and LOX (alox12↓ → MDA↓) pathways, while upregulating the CYP450 pathway (cyp2j↑ → 11,12-EET↑). Probiotics also enhanced Fe³⁺ sequestration (steap4↑) and antioxidant defense (CAT↑, gpx4a↑), limiting Fenton reaction-mediated oxidative injury, and restored hepatic TG synthesis through upregulation of the DHAP-to-TG cascade (DHAP—(gpd1b↑) → G3P↑—(gpat3↑) → LPA—(agpat6↑) → PA—(plpp7↑) → DAG↑—(dgat2↑) → TG↑). These findings suggest that NP induces hepatotoxicity in S. meridionalis, involving ferroptosis, AA metabolism disruption and impaired TG synthesis as interconnected pathological events. Probiotics likely counteract this toxicity through systemic metabolic reprogramming. Collectively, these findings elucidate the hepatotoxic mechanisms of NP in S. meridionalis and offer toxicological data for its risk assessment, supporting the potential of probiotic-based strategies to mitigate emerging pollutant impacts in aquatic organisms.

Nonylphenol (NP) bioremediation is constrained by the scarcity of efficient and non-pathogenic degrading strains. To clarify the role of acetyl-CoA C-acetyltransferase (AtoB) in NP degradation, we generated an atoB-overexpressed strain (LY-OE) from the environmentally tolerant Bacillus cereus LY and compared its degradation rate with the wild type using HPLC. Untargeted lipidomics was conducted to characterize metabolic responses under NP stress, and key differential lipid metabolites (DELMs) were further validated by ELISA. Additionally, AtoB concentration and ATP content were quantified using commercial assay kits in Bacillus cereus. LY-OE showed a markedly higher NP degradation rate (96%) than LY (85%). Lipidomic analysis identified 34 significant DELMs (VIP > 1, p < 0.05), including elevated cardiolipin (CL) and phosphatidylglycerol (PG), and reduced phosphatidylcholine (PC) and triglycerides (TG). ELISA confirmed these changes (p < 0.01 or p < 0.001), consistent with lipidomic findings. LY-OE showed significantly higher AtoB concentration during the logarithmic growth phase and exhibited higher ATP content during NP degradation. These findings suggest that atoB overexpression enhances NP degradation by both boosting energy supply and remodeling lipid metabolism. This work identifies atoB as a key factor for NP biodegradation and provides a promising strategy for developing high-performance bioremediation strains.

4-Nonylphenol (4-NP), an important fine chemical precursor, can cause endocrine disruption, resist natural degradation, and bioconcentrate. Biodegradation is an effective and environmentally sustainable approach to its remediation. This study employed a mixture comprising equal proportions of six non-pathogenic Bacillus strains to screen and identify strains capable of degrading 4-NP, and degradation rate was measured using an ELISA kit, and metabolomic analyses and whole-genome sequencing were used to investigate the response of Bacillus to 4-NP and elucidate pathways involved in 4-NP degradation. The results revealed DY and LY strains isolated at 500 μg/L 4-NP. The DY strain was identified as Bacillus thuringiensis, and the LY strain was identified as Bacillus cereus via physiological, biochemical and PCR analyses. The degradation efficiency of a DY and LY strain mixture was 79.45% after 7 days. At 1000 μg/L 4-NP, only the LY strain was successfully isolated. Whole-genome sequencing indicated that the LY strain (accession number: CRA021210) shares the highest homology with B. cereus strain FORC-047. Notably, it showed a degradation rate of 86.34% after 7 days. Metabolomics analysis indicates that 4-NP affects the degradation pathways of aromatic compounds and benzoic acid in B. cereus. Combined with genome data, it is hypothesized that the 4-NP degradation pathway involves its conversion to p-hydroxybenzoic acid, catalyzed by monooxygenases, dioxygenases and oxidases. Subsequently, p-hydroxybenzoic acid degrades via one of two potential pathways: it produces phenol through decarboxylase or is oxidized to benzoic acid by monooxygenase. In summary, the DY and LY strains are capable of degrading 4-NP. Furthermore, we postulate potential 4-NP degradation pathways, providing insights for the remediation of 4-NP in aquatic environments.