Transcriptomics reveal the antibiofilm mechanism of NaCl combined with citral against Vibrio parahaemolyticus.

Vibrio parahaemolyticus (VP) as a prominent foodborne pathogen in seafood generally adheres to various surfaces and forms biofilms in the processing of aquatic products. The study aimed to elucidate the inhibitory efficacy and potential mechanism of salinity (NaCl) or it combined with citral against the biofilm formation of VP. Three VP strains formed the most biofilm at 1.0% NaCl, and their biofilms gradually declined with the increase of NaCl concentration. Compared with 1% NaCl, applying 3% and 5% NaCl or NaCl in combination with citral at 10-40 µg/mL significantly reduced biofilm biomass, cellular activity, and viable cells, as well as extracellular polymeric substances (EPS) and cell surface hydrophobicity. Sparser and thinner VP biofilm with large dead cells were observed under the combined treatment, in contrast to the dense architectures of biofilm formed at 1% NaCl. Although VP exhibited the strongest swimming and swarming ability at 3% NaCl, the two motilities were both significantly reduced by citral for all three salinities. Transcriptomic profiling revealed that, compared with 1% NaCl (Con), the two treatments consisting of 3% NaCl (Sal3) and it combined with 40 µg/mL citral (Com) drastically altered gene expression patterns in VP biofilm cells, resulting in 1196 and 1304 differentially expressed genes, respectively. The treatment of Com group altered the transcription of various genes related to chemotaxis, flagellar assembly, EPS synthesis, LuxS and CqsA-mediated quorum sensing, and c-di-GMP, which might interfere with biofilm development of VP. Our findings provided novel insights into the combined regulatory mechanism of high salinity and citral for antibiofilm formation in VP. KEY POINTS: • High salinity enhanced the antibiofilm efficacy of citral against Vibrio parahaemolyticus. • Combined treatment downregulated the expression of exopolysaccharide synthesis genes. • A total of 3% NaCl and combined treatments interfered with signaling pathways of QS and c-di-GMP.

An improved up-conversion nanoparticles-based immunochromatographic assay for rapid detection of zearalenone in cereals.

A novel improved up-conversion nanoparticles-based immunochromatographic assay (IUCNPs-ICA) was developed for the detection of zearalenone (ZEN). Lu3+-doped UCNPs were synthesized using the solvothermal method, and the UCNPs doped with 30 % Lu3+ displayed optimal optical properties. The IUCNPs-ICA was subsequently developed for the detection of ZEN in cereals under optimized conditions. The detection time and limit of detection (LOD) were 10 min and 0.1 µg/L, respectively. Moreover, a good linear relationship was observed from 0 to 100 µg/L ZEN (r2 = 0.9946) and high specificity for other mycotoxins. LODs in spiked maize and wheat reached 0.16 µg/kg, and recovery rates were 82.11-100.76 % and 79.64-98.51 %. There was good consistency between the results of IUCNPs-ICA, colloidal gold-ICA, and high-performance liquid chromatography (HPLC) in the detection of natural cereal samples. The collective results support the utility of IUCNPs-ICA as a reliable on-site screening method for ZEN residue analysis in various cereals.