This study aimed to establish the mode of binding between Quercetin (QEN) and an essential protein called ClfB in forming biofilm in Staphylococcus aureus (S. aureus). In this study, the raw data of GSE163153 were analyzed for quality control, alignment, and gene counts, and the differential analysis detected the key differentially expressed genes (DEGs) assisting in the formation of the S. aureus biofilm. Then, the protein-protein interaction (PPI) and gene function enrichment analyses of the target genes, identified a gene called clfB to be closely related to biofilm formation. ClfB was structurally characterized, molecularly docked, and kinetically simulated to unravel the mode of binding of QEN to ClfB. Meanwhile, the growth curve and transmission electron microscopy methods examined the effect of QEN on the S. aureus growth. Results indicated that the clfB gene was increasingly expressed during biofilm formation and was involved in cell adhesion, pathogenicity, and infection. We identified 5 amino acid sites of ClfB (D272, R331, I379, K391, E490) as potential sites for binding QEN, which would indirectly influence the changes in the functional sites N234, D270, Y273, F328, inhibiting the formation of biofilm. Meanwhile, 128 μg/ml of QEN could significantly inhibit the S. aureus biofilm formation. This manuscript serves as a molecular foundation for QEN as an antibacterial drug providing a new perspective for developing antibacterial drugs.
hotpot; thus, the hotpot oil needs to be of high quality.Currently, Sichuan and Chongqing HSs are the two most popular HS types in China. Most HSs for Sichuan hotpot are prepared from beef tallow, which gives the HS its strong beef tallow flavor. However, beef tallow is high in saturated fatty acids and cholesterol. A high intake of these HSs may cause obesity, hyperlipidemia, and atherosclerosis, which significantly
Increasingly, alternatives to antibiotics are being used to mitigate the rapid onset and development of bacterial resistance, and the combination of natural compounds with traditional antibiotics has become an effective therapeutic strategy. Therefore, we attempted to discover more mechanisms to restore susceptibility and effective dosing strategies.
Introduction
Staphylococcus aureus
(
S. aureus
) is a common cause of mastitis in dairy cows, a condition that has a significant economic impact.
S. aureus
displays quorum sensing (QS) system-controlled virulence characteristics, like biofilm formation, that make therapy challenging. In order to effectively combat
S. aureus
, one potential technique is to interfere with quorum sensing.
Methods
This study evaluated the effects of different Baicalin (BAI) concentrations on the growth and the biofilm of
S. aureus
isolates, including the biofilm formation and mature biofilm clearance. The binding activity of BAI to LuxS was verified by molecular docking and kinetic simulations. The secondary structure of LuxS in the formulations was characterized using fluorescence quenching and Fourier transform infrared (FTIR) spectroscopy. Additionally, using fluorescence quantitative PCR, the impact of BAI on the transcript levels of the
luxS
and biofilm-related genes was investigated. The impact of BAI on LuxS at the level of protein expression was also confirmed by a Western blotting investigation.
Results
According to the docking experiments, they were able to engage with the amino acid residues in LuxS and BAI through hydrogen bonding. The results of molecular dynamics simulations and the binding free energy also confirmed the stability of the complex and supported the experimental results. BAI showed weak inhibitory activity against
S. aureus
but significantly reduced biofilm formation and disrupted mature biofilms. BAI also downregulated
luxS
and biofilm-associated genes’ mRNA expression. Successful binding was confirmed using fluorescence quenching and FTIR.
Discussion
We thus report that BAI inhibits the
S. aureus
LuxS/AI-2 system for the first time, which raises the possibility that BAI could be employed as a possible antimicrobial drug to treat
S. aureus
strain-caused biofilms.
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