Effect of RNAⅢ inhibitor peptide on the expression of virulence factors of Staphylococcus aureus at different growth phases
ZHOU Ying1 HOU Zheng2 XUE Xiaoyan2 WEI Ming1 LI Fen1 YAO Jia3 ZHANG Ye3 WANG Yang3
1.Department of Pharmacology, Xi’an Medical University, Shaanxi Province, Xi’an 710021, China;
2.Department of Pharmacology, Air Force Medical University, Shaanxi Province, Xi’an 710032, China;
3.Molecular Virology and Viral Immunology Laboratory, Xi’an Medical University, Shaanxi Province, Xi’an 710021, China
Abstract：Objective To explore the role of RNAⅢ inhibitory peptide (RIP) in regulating the expression of staphylolysin and adhesion-related proteins at different growth phases. Methods The methicillin-resistant Staphylococcus aureus was inoculated to medium proportionally, and the bacteria cultured overnight were transferred to TSB medium (containing 0.5% glucose), respectively, and the concentration was adjusted to 1×108 CFU/mL. The RIP group was added with RIP derivatives (RIP1183) designed and synthesized by research group, while the control group was added with sterile phosphate buffer. Its effects on the growth curve and biofilm formation were examined. Quantitative real-time fluorescence polymerase chain reaction was used to detect the expression levels of RNAⅢ, human leucocyte antigen (HLA), icaA, and fnbA during the bacterial retardation phase (2 h), logarithmic phase (6 h), and stable phase (10 h), and compared with the control group. Results Compared with the control group, RIP1183 did not affect the growth of bacteria, and the difference was not statistically significant (P ＞ 0.05). Compared with the control group, the formation of bacterial biofilms in the RIP group was significantly reduced (P ＜ 0.01). In the bacterial retardation phase (2 h), the expression of RNAⅢ in RIP group was obviously decreased (P < 0.05). In the logarithmic phase (6 h), compared with the control group, the expression of RNAⅢ and HLA were obviously decreased (P ＜ 0.01). In the stable phase (10 h), the expression of icaA, fnbA and RNAⅢ were obviously decreased (P ＜ 0.05 or P ＜ 0.01). Conclusion RIP1183 inhibits the expression of RNAⅢ, an effector molecule of the accessory gene regulation system, and significantly reduces the expression of different virulence factors in different phases, thereby destroying the mechanism of bacteria’s adaptation to the environment, which may be one of the mechanisms of its antibacterial activity and anti-biofilm formation.
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2020, Vol. 17 
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