题目：Why can’t the obligate anaerobe grow in the aerobic environment?

报告人：路争，美国伊利诺伊大学香槟校区博士后

时间：2018年4月4日上午9:00

地点：生科楼414

摘要：

Life evolved in an anoxic world. Ferrous iron was readily available, and its proficiency as a surface and electron-transfer catalyst resulted in its recruitment into many enzymes.  

Two billion years later, the appearance of oxygenic photosystem II put organisms at risk, because oxygen oxidizes redox enzymes to make reactive oxygen species (ROS), and the ROS can then poison the exposed iron cofactors of enzymes.  

Microbes display profound differences in their tolerance for oxygen, and this trait organizes the structure of many microbial communities. However, the molecular basis of oxygen sensitivity is not well understood.  We determined that Bacteroides thetaiotaomicron, an abundant member of the human intestinal flora, is incapacitated by superoxide stress when it enters a fully oxic environment.  The key difference from oxygen-tolerant bacteria lies not in its defensive systems, nor in the nature of the affected enzymes, but in the rate of endogenous oxidant formation. Anaerobes thrive in oxygen-poor environments because they deploy low-potential electron-transfer pathways; these results suggest that an ancillary effect is the reactivity of these pathways with oxygen,thereby generating enough ROS to preclude oxic growth.

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