Quorum sensing (QS) is a process of bacterial communication that has been a novel target for drug discovery. Pyocyanin quantification assay confirmed that resveratrol was an effective quorum sensing inhibitor (QSI) against Pseudomonas aeruginosa PAO1. In this study, the global metabolite changes of P. aeruginosa PAO1 exposed to QSI resveratrol were investigated by H NMR spectroscopy. A total of 40 metabolites containing amino acids, organic acid, organic amine, and energy storage compounds were identified. The changed metabolic profile indicated that resveratrol influenced pathways including oxidative stress, protein synthesis, and energy metabolism. Oxidative stress could upregulate the expression of genes related to QS in P. aeruginosa. It suggested that resveratrol could inhibit the QS systems in P. aeruginosa PAO1 by relieving oxidative stress due to its antioxidant activity. On the other hand, resveratrol could attenuate the pathogenicity of P. aeruginosa PAO1 by disturbing the TCA cycle so that anaerobic respiration could suppress the virulence because anaerobiosis could induce the loss of cytotoxicity regulated by QS in P. aeruginosa. These findings deepened our comprehending of the metabolic responses of P. aeruginosa PAO1 to resveratrol and pinpointed the possible underlying mechanism of resveratrol's inhibition effect on QS in P. aeruginosa PAO1.

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Biofilm formation is regarded as one of the major determinants in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) as pathogens of medical device-related infection. However, methicillin-susceptible S. aureus (MSSA) can also form biofilm in vitro and such biofilms are resistant to vancomycin. Hence, researching the possible mechanisms of MSSA biofilm formation is urgent and necessary. Here, we used S. aureus ATCC25923 as the model strain, and studied gene expression profiles in biofilms after the treatment of ursolic acid and resveratrol using RNA-seq technology. The results showed that only ursolic acid could inhibit biofilm formation, which differed from their applied on the multiple clinical drugs resistant MRSA biofilm. RNA-seq data was validated by examining the expression of six genes involved in biofilm formation by qRT-PCR. These data analysis indicated that the mechanism of the MSSA biofilm formation was different from that of the MRSA, due to absence of accessory gene regulator (agr) function. These findings suggest that biofilms of S. aureus with agr dysfunction may be more resistant than those with agr function. Therefore, the infection from clinical MSSA may be recalcitrant once forming biofilm. Further study is necessary to uncover the mechanisms of biofilm formation in other clinical S. aureus.

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Environmental contextHeavy metals are non-degradable and are therefore a severe and persistent environmental menace. The toxic effects of Pb were investigated using NMR to determine the metabolic changes in earthworms exposed to Pb. The approach using 1H NMR to analyse earthworm metabolomics demonstrated great potential as a reliable, rapid and convenient tool to assess the toxicity of heavy metals and could be used to identify warning signs of heavy metal contamination of soil. AbstractA 1H nuclear magnetic resonance (NMR)-based approach to metabolomics combined with atomic absorption spectroscopy, histopathological examination and biochemical assessment was used to determine the toxic effects of lead (Pb) on earthworms (Eisenia fetida). Earthworms were exposed to Pb in a lead nitrate solution at converted concentrations of 1.25, 5.0 and 20µgcm–2 in contact tests for 48h. Based on histopathological inspection, the epidermis, muscles, chloragogenous tissues and intestinal epithelium were severely impaired. Based on biochemical assessment, a disruption of the antioxidative system and neurotoxic effects in earthworms occurred following exposure to Pb. Orthogonal signal correction–partial least-squares-discriminant analysis of NMR profiles indicated that Pb exposure in earthworms caused widespread metabolic changes, which were associated with oxidative stress, neurotransmitter imbalance, disruption of osmotic equilibrium and interference in energy metabolism and nucleic acid metabolism. The integrated metabolomics approach provided new insights into Pb-induced toxicity in earthworms. Metabolomics is a powerful and highly effective approach and has great promise to determine the ecotoxicological effects and the underlying mechanisms of toxicity of heavy metals.