Phenotype and RNA-seq-Based transcriptome profiling of Staphylococcus aureus biofilms in response to tea tree oil.

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that causes a wide range of diseases, including food poisoning. Tea tree oil (TTO), an essential oil distilled from Melaleuca alternifolia, is well-known for its antibacterial activities. TTO effectively inhibited all 19 tested strains of S. aureus biofilm and planktonic cells. Phenotype analyses of S. aureus biofilm cells exposed to TTO were performed by biofilm adhesion assays, eDNA detection and PIA release. RNA sequencing (RNA-seq) was used in our study to elucidate the mechanism of TTO as a potential antibacterial agent to evaluate differentially expressed genes (DEGs) and the functional network in S. aureus ATCC 29213 biofilms. TTO significantly changed (greater than a 2- or less than a 2-fold change) the expression of 304 genes in S. aureus contained in biofilms. The levels of genes related to the glycine, serine and threonine metabolism pathway, purine metabolism pathway, pyrimidine metabolism pathway and amino acid biosynthesis pathway were dramatically changed in the biofilm exposed to TTO. Furthermore, the expression changes identified by RNA-seq analysis were verified by real-time RT-PCR. To the best of our knowledge, this research is the first study to report the phenotype and expression profiles of S. aureus in biofilms exposed to TTO.

Antioxidative and anticancer properties of Licochalcone A from licorice.

ETHNOPHARMACOLOGICAL RELEVANCE: Licochalcone A (LCA) is a characteristic chalcone that is found in licorice, which is a traditional medicinal plant. In traditional medicine, LCA possesses many potential biological activities, including anti-parasitic, anti-inflammatory and antitumor activities. AIM OF THE STUDY: To determine the antioxidant activity of LCA and, on this basis, to investigate the role of its anticancer activity. MATERIALS AND METHODS: To validate the antioxidant activity of LCA, the proteins SOD, CAT and GPx1 were analyzed using western blotting and cellular antioxidant activity (CAA) assays. Oxidative free radicals are associated with cancer cells. Therefore, the anticancer activity of LCA was also evaluated. To assess the anticancer activity, cell viability assays were performed and apoptosis was evaluated. In addition, MAPK-related proteins were analyzed using western blotting. RESULTS: The experimental data showed that the EC50 of LCA is 58.79±0.05µg/mL and 46.29±0.05µg/mL under the two conditions tested, with or without PBS. In addition, LCA at a concentration of approximately 2-8µg/mL can induce the expression of SOD, CAT and GPx1 proteins. Further, LCA inhibits the growth of HepG2 cells through cell proliferation arrest and the subsequent induction of apoptosis, and LCA attenuated the p38/JNK/ERK signaling pathway in a dose-dependent manner. CONCLUSION: The results showed that LCA suppresses the oxidation of cells and markedly inhibits the proliferation of cancer cells. These findings confirm the traditional use of LCA in folk medicine.