SpxB-mediated H2O2 induces programmed cell death in Streptococcus sanguinis

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• 作者：Ting Li ; Shuheng Zhai ; Mengya Xu ; Mengmeng Shang ; Yu Gao ; Gangshan Liu ; Qingxuan Wang and Lanyan Zheng
• 刊名：Journal of Basic Microbiology
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：56
• 期：7
• 页码：741-752
• 全文大小：1166K
• ISSN：1521-4028

文摘

Streptococcus sanguinis (S. sanguinis) is a commensal oral streptococci that produces hydrogen peroxide (H₂O₂), and this production is dependent on pyruvate oxidase (SpxB) activity. In addition to its well-known role in intraspecies or interspecies competitions, recent studies have shown that H₂O₂ produced by S. sanguinis under aerobic conditions not only upregulates biofilm formation and eDNA release but also regulates cell death without obvious cell lysis. Here, we report that S. sanguinis exhibits characteristic hallmarks of eukaryotic apoptosis when it encounters endogenous and exogenous H₂O₂. As the most common mode of programmed cell death (PCD), apoptosis is accompanied by a series of biochemical and morphological events, including DNA fragmentation, chromosome condensation, membrane potential depolarization, phosphatidylserine (PS) exposure, and caspase substrate binding protein activity changes. In addition, we also provide genetic evidence that there is decreased expression of the related DNA repair genes comEA, recA, dnaC, dinG, and pcrA in the wild-type compared to the isogenic spxB mutant in S. sanguinis. Our data suggest that endogenous H₂O₂ is the most important agent in this development process in S. sanguinis.