Harnessing the endophytic Clavispora lusitaniae for the biogenic synthesis of ethylene glycol-capped cerium oxide nanoparticles: a green approach to combat respiratory Pseudomonas aeruginosa

BACKGROUND: The utilization of endophytes as specialized microbial cell factories offers a sustainable and high-efficiency platform for the biosynthesis of functionalized nanomaterials. This study investigates the potential of a novel endophytic yeast, Clavispora lusitaniae, to produce cerium oxide nanoparticles (CeO₂NPs) and evaluates their efficacy against extensively drug-resistant (XDR) P. aeruginosa. RESULTS: An endophytic yeast, C. lusitaniae, was isolated for the first time from the medicinal plant Artemisia judaica and employed for the biosynthesis of CeO₂NPs, followed by surface capping with ethylene glycol (EG) to modify the nanoparticle surface properties. The synthesized nanoparticles were characterized using UV-Vis, FTIR, XRD, TEM, and DLS. These analyses confirmed the formation of spherical EG-CeO₂NPs with an average size of 8-20 nm. EG-CeO₂NPs exhibited strong antibacterial activity against XDR P. aeruginosa strains, with a minimum inhibitory concentration ranging from 0.6 to 1.25 mg/mL. Furthermore, these nanoparticles demonstrated potent anti-biofilm efficacy, achieving reductions of up to 89%. Mechanistic investigations demonstrated that EG-CeO₂NPs disrupt bacterial cell membranes, leading to intracellular protein leakage and elevated lipid peroxidation (indicated by increased malondialdehyde levels). Furthermore, the expression levels of quorum sensing (e.g., lasR and rhlR) and virulence-associated genes (e.g., toxA and exoS) were markedly downregulated by up to 87% compared to untreated controls. CONCLUSIONS: This study establishes C. lusitaniae as a robust microbial cell factory for synthesizing functionalized CeO₂NPs with potent activity against XDR P. aeruginosa. Our results demonstrate the potential of microbial bioprocessing in engineering prospective nanotechnological platforms to combat antimicrobial resistance. However, further studies evaluating colloidal behavior under physiologically relevant conditions, mammalian-cell cytotoxicity, and in vivo efficacy are required before biomedical translation.