胱氨酸/半胱氨酸调控活性氧代谢影响大肠杆菌耐药性

Impact of cystine/cysteine on drug resistance of Escherichia coli by regulating ROS metabolisms

摘要:

【背景】随着越来越多超级细菌出现和抗生素资源的渐渐枯竭，细菌耐药机制研究愈加重要。【目的】探讨大肠杆菌内源半胱氨酸推动Fenton反应，调控胞内的活性氧水平，从而影响细菌耐药性这一代谢途径。【方法】在贫硫的培养条件下，通过控制外源胱氨酸和抗生素浓度，研究了胱氨酸/半胱氨酸对大肠杆菌耐药性的影响。【结果】较低水平的半胱氨酸使大肠杆菌对抗生素的耐药性增强，RNA-Seq的结果证明了胱氨酸内流对Fur、CysB和SOS的调控作用。LC-MS对外流硫醇的分析显示，细胞会快速将过量内流的半胱氨酸泵出胞外。在抗生素一定浓度范围内，半胱氨酸外排泵AlaE表现出良好的细胞保护作用。【结论】大肠杆菌对不同作用机理抗生素硫酸庆大霉素、氨苄青霉素和诺氟沙星的耐药性均受内源半胱氨酸水平的影响。本文通过研究半胱氨酸调控活性氧代谢对大肠杆菌耐药性的影响，为探讨细菌耐药性机制提供新的理论依据。

Abstract:

[Background] With increasing numbers of drug resistant microorganisms and drained antibiotics sources, research on bacterial drug resistance mechanisms has risen to be a most urgent scientific topic. [Objective] To understand how endogenous cysteine affects ROS levels in Escherichia coli by promoting the Fenton reaction. [Methods] The effect of cysteine on the antibiotic resistance of E. coli was investigated by controlling the concentration of exogenous cystine and the concentration of antibiotics (gentamicin, ampicillin, norfloxacin) under poor sulfur conditions. [Results] Low concentrations of cysteine increased drug resistance of E. coli to all of the antibiotics used in this study. The regulation on Fur, CysB or SOS by influx of cystine was also confirmed using RNA-Seq. An analysis of sulfur efflux by LC-MS showed that excess cysteine was excluded immediately. At certain concentrations of antibiotics, the efflux pump AlaE exhibited favorable protection on cells. [Conclusion] Drug resistance of E. coli to gentamicin, ampicillin, norfloxacin, antibiotics with different mechanisms of action, was affected by endogenous cysteine levels. Our current work provides new theoretical information on bacterial drug-resistance mechanisms.