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Different organic compounds can have varying degrees of impact on the activity of Lactobacillus paracasei. The study focused on the impact and action mechanism of different organic selenium products on the bioactivity of two strains of L. paracasei. The growth, antioxidant activity, extracellular polysaccharide secretion, quorum sensing (QS), and biofilm formation of the strains before and after the addition of organic selenium crude products and three organic selenium standard were evaluated. The results showed that the addition of crude organic selenium promoted the various activities of the strain. l‐selenocysteine had the strongest regulatory effect, with maximum GIM1.80 biofilm formation when it reached a critical concentration of 0.4 μg/mL; l‐selenomethionine resulted in the highest activity of the signal molecule Auto inducer‐2 of GDMCC1.155, when it reached a critical concentration of 0.4 μg/mL. The results of scanning electron microscopy demonstrated that the addition of organic selenium effectively improved the morphological structure of the two bacterial cells. Molecular docking revealed that the mechanism by which organic selenium regulates QS in Lactobacillus was achieved by binding two crucial receptor proteins (histidine protein kinase HKP and periplasmic binding protein LuxP) from specific sites. Furthermore, organic selenium products have a beneficial regulatory effect on the biological activity of L. paracasei. Overall, these findings provide a new alternative (organic selenium) for regulating the viability and beneficial activity of L. paracasei. Significance Statement: The study found that organic selenium can promote the growth, antioxidant activity, and biofilm formation of Lactobacillus by activating quorum sensing (QS). Uniquely, organic selenium can both positively and negatively regulate QS and biofilm formation of Lactobacillus, and critical concentrations have also been obtained. Furthermore, the regulating mechanism of organic selenium on the activity of Lactobacillus was revealed. This study provides a new alternative for regulating and stimulating the beneficial activity of probiotics. [ABSTRACT FROM AUTHOR]

Introduction: The opportunistic pathogen Candida albicans can form biofilms, resulting in drug resistance with great risk to medical treatment. Methodology: We investigated the ability of C. albicans to form biofilms on different materials, as well as the inhibitory and eradicating effects of cordycepin on biofilm. The action mechanism of cordycepin against biofilm was studied by crystal violet staining, XTT [2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide] reduction method, phenol-sulfuric acid method, cellular superficial hydrophobicity (CSH) assay, and confocal laser scanning microscope observation. We also evaluated the acute toxicity of cordycepin in vivo. Results: The results showed facile formation of biofilms by C. albicans on polypropylene. The 50% minimum inhibitory concentration (MIC50) of cordycepin was 0.062 mg/mL. A concentration of 0.125 mg/mL significantly decreased biofilm formation, metabolic activity, secretion of extracellular polysaccharides, and relative CSH. Cordycepin could inhibit biofilm formation at low concentration without affecting fungal growth. In addition, cordycepin effectively eradicated 59.14% of mature biofilms of C. albicans at a concentration of 0.5 mg/mL. For acute toxicity, the LD50 (50% of lethal dose) of cordycepin was determined as higher than 500 mg/kg for mice. Conclusion: The results of this study show that cordycepin significantly inhibited and eradicated biofilms by decreasing metabolic activity, the ratio of living cells, the hydrophobicity, and damaging the extracellular polysaccharides of biofilm. These findings should facilitate more effective application of cordycepin and suggest a new direction for the treatment of fungal infections. [ABSTRACT FROM AUTHOR]

Cell-to-cell communication or quorum sensing (QS) leads to biofilm formation and causing other virulence factors which are extreme problems for food safety, biofilm related infectious diseases etc. This study evaluated the anti-QS activity of the Amomum tsaoko extract (0.5–4 mg/ml) by using Chromobacterium violaceum a biosensor strain and biofilm formation by crystal violate assay. Experimental results demonstrated that the overall yield of Amomum tsao-ko extract was 11.33 ± 0.3% (w/w). MIC for Staphylococcus aureus (Gram positive), Salmonella Typhimurium and Pseudomonas aeruginosa (Gram negative) was 1, 2 and 2 mg/ml, respectively. A concentration of 4 mg/ml extract showed highest biofilm inhibition 51.96% on S. Typhimurium when 47.06%, 45.28% were shown by S. aureus , P. aeruginosa respectively . The damage of biofilm architecture was observed by Confocal Laser Scanning Microscopy (CLSM). A level of 44.59% inhibition of violacein production was demonstrated when the dose was 4 mg/ml. Swarming motility inhibition was observed in a dose dependent manner. Taken together, the treatment of A. tsaoko extract can deliver value to food product and medicine by controlling pathogenesis. [ABSTRACT FROM AUTHOR]

Abstract: Enrichment of burdock leaf components and the inhibition effect of the obtained 7 burdock leaf fractions on formation of biofilm have been evaluated for the first time. Firstly, burdock leaf fractions were obtained though separation of burdock leaf extracts by macroporous resin column chromatography, and four fractions were obtained, namely, water elution fraction, 20%, 34% and 70% ethanol eluted fractions. It was found that the 20% and 34% ethanol fractions both significantly inhibited the formation of biofilm by Escherichia coli, with IC50 of 1.10 and 1.01 mg/ml, respectively. The 70% ethanol elution fraction exhibited the strongest inhibitory activity against biofilm formation with an IC50 of 0.017 mg/ml. In order to obtain more fractions with higher inhibitory activity, polyamide resin was used to further purify the 34% ethanol elution fraction. The second chromatography separation significant improved the activity of burdock leaf fractions and the IC50 of a new fraction was 0.03 mg/ml. The phenolic contents of the fractions ranged from 7.5 to 369.7 mg/g and there was a high correlation between the anti-biofilm capacity and phenolic contents, except for 70% ethanol fraction. Scanning electron microscopy (SEM) observation showed that there was no biofilm formation for cultures treated with burdock leaf fraction, conforming the significant inhibition activity of burdock leaf fraction against the formation of biofilm. The results suggest that separation and enrichment of the active ingredients could significantly improve the activities of fractions and the obtained burdock leaf fractions provide new alternatives for control of biofilms. [Copyright &y& Elsevier]