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Abstract
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.
Credit Author Statement
Conceptualization and supervision, Guiqin Wang; Software and visualization, Yanni Mao and Panpan Liu; Investigation, Haorong Chen and Yuxia Wang; Project administration, Caixia li; Writing—original draft preparation, Yanni Mao; Writing—review and editing, Guiqin Wang. All authors contributed significantly to the work that was published, whether it be in the ideation, study design, implementation, data collection, analysis, and interpretation, or in all of these areas. They also all participated in writing, revising, or critically evaluating the article, gave their final approval for the version that would be published, agreed on the journal to which the article would be submitted, and agreed to be responsible for all aspects of the work.
Data Sharing Statement
The corresponding author can provide the data that back up the study’s findings upon reasonable request.
Acknowledgments
We acknowledge the assistance of all the instructors and students in conducting our experiment, as well as the contributions of all the writers of this paper. We appreciate the gifts of V. harveyi BB152 and V. harveyi BB170 from Professors Yongjie Liu of Nanjing Agricultural University and Prof. Xiangan Han of Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences. Additionally, I’d like to thank MJEditor (www.mjeditor.com) for providing English editing services during the production of this manuscript as well as all the reviewers who took part in the review.
Disclosure
The study’s authors affirm that there were no financial or commercial ties that might be viewed as having a potential conflict of interest. The authors report that they have no competing interests.