生物分子进化史上的最大变化之一是由无氧大气变为含有大量氧的大气。这种变化开始于海洋中以含有叶绿素的绿色杆菌为主要生物的时期。约在20亿年前,大气中的氧浓度增至0.02%,4亿年前增至20%,因此,以前唯一的生命形式厌氧微生物面临以下抉择:通过进化产生抗氧化物以保护自身免受分子氧的破坏或退避到无氧环境中。一些厌氧菌如梭状芽孢杆菌采取了后一种 One of the biggest changes in the history of the evolution of biomolecules is the change from anaerobic atmosphere to an atmosphere containing a large amount of oxygen. This change began with the oceans in the chlorophyll-containing green bacilli as the main biological period. About 2 billion years ago, the concentration of oxygen in the atmosphere increased to 0.02% and increased to 20% 400 million years ago. As a result, the only life-form anaerobic microorganisms faced the following choices: to produce antioxidants by evolution to protect themselves By the molecular oxygen damage or retreat to anaerobic environment. Some anaerobic bacteria such as Clostridium take the latter