选择性σ因子SigF影响耻垢分枝杆菌的抗氧化能力

Sigma factor F regulates Mycobacterium smegmatis hydrogen peroxide resistance

摘要:

摘要:【目的】σ因子是细菌RNA 聚合酶全酶的重要组分，包括必须σ 因子和选择性σ因子。SigF作为重要的选择性σ因子影响结核分枝杆菌(Mycobacterium tuberculosis)的致病性和毒力等重要的功能。与之对应的在非致病性、快速生长的分枝杆菌耻垢分枝杆菌(M．smegmatis)中，sigF的调控可能与其适应一定的生理环 境相关。【方法】通过基因敲除、遗传互补和抗药性分析，系统的研究了耻垢分枝杆菌SigF 的应答调控。【结果】sigF 敲除菌株与野生菌相比，对过氧化氢特别敏感，并且这种敏感性能够通过反式互补野生型的基因得到回复;由于细菌体内的抗氧化能力与耐药性有较高的相关性，进一步分析sigF 敲除菌株的抗药性和抗氧化相关基因的表达情况，显示SigF 影响细菌清除过氧化氢的能力，但是并不影响包括异烟肼等药物的敏感性及与异烟肼敏感性相关基因的表达。【结论】SigF 调控的活性氧胁迫应答途径与异烟肼活化的氧化胁迫应答途径不同。另外，实验显示SigF 参与了耻垢分枝杆菌的色素的合成，提示SigF 参与的是光氧化胁迫应答途径，与药物引起的氧化胁迫应答途径是不同的通路。

Abstract:

Abstract:［Objective］ A sigma factor is an important component of RNA polymerase complex and is essential for initiation of RNA synthesis． The sigma factors fall into 2 categories: primary sigma factor is essential for bacterial growth and the alterative sigma factor is activated under different environmental conditions． Sigma F (SigF) is one of the sigma factors of Mycobacterium tuberculosis，affecting its virulence and pathogenesis． In contrast，the ortholog of the nonvirulent，fast growing strain Mycobacterium smegmatis has been suggested without similar physiology roles． Here，we studied the functions of M． smegmatis SigF． ［Methods］sigF knockout Mycobacterium smegmatis strain was constructed by specialized transduction． The wild type，knockout and complementary stains were challenged by oxidative stress and antibiotics． ［Results］The knockout sigF stain was susceptible oxidative stress，compared to wild type． Furthermore，there was no defect in resistance to antibiotics including isoniazid between the knockout sigF strain and wild type strain． In addition，SigF is required for carotenoid pigment production in M． smegmatis． ［Conclusion］ Our data suggested that SigF is important to detoxify the reactive oxygen species，probably through photo-oxidative stress response pathway，which is independent on the pathway that is required for the isoniazid activation.