万物简史 第423期:生命的起源(17)

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　　For two billion years bacterial¹ organisms were the only forms of life. 在20亿年时间里，细菌是惟一的生命形式。

　　They lived, they reproduced, they swarmed², but they didn't show any particular inclination³ to move on to another, more challenging level of existence. 它们活着，它们繁殖，它们数量增加，但没有表现出想发展展到另一个更富挑战性的生存层面的特别倾向。

　　At some point in the first billion years of life, cyanobacteria, or blue-green algae⁴, 在生命的头10亿年的某个时候，藻青菌，或称蓝绿藻，

　　learned to tap into a freely available resource—the hydrogen that exists in spectacular abundance in water. 学会了利用大量存在的资源——存在于水中的特别丰富的氢。

　　They absorbed water molecules⁵, supped on the hydrogen, and released the oxygen as waste, and in so doing invented photosynthesis⁶. 它们吸叫水分子，吃掉了氢，排出了氧，在此过程中发明了光合作用。

　　As Margulis and Sagan note, photosynthesis is "undoubtedly⁷ the most important single metabolic⁸ innovation in the history of life on the planet" 正如马古利斯和萨根指出的，“光合作用无疑是本星球的生命史上所创造的最重要的新陈代谢方法”

　　and it was invented not by plants but by bacteria. 光合作用是由细菌而不是由植物发明的。

　　As cyanobacteria proliferated⁹ the world began to fill with O2 to the consternation¹⁰ of those organisms that found it poisonous—which in those days was all of them. 随着藻青菌的增多，世界开始充满氧气，发现氧是有毒的微生生深感吃惊——而在那个年代，那种微生物比比皆是。

　　In an anaerobic¹¹ (or a non-oxygen-using) world, oxygen is extremely poisonous. 在一个厌氧的（或不使用氧的）世界里，氧是剧毒的。

　　Our white cells actually use oxygen to kill invading bacteria. 我们的白血球实际上就是氧来杀死入侵的细菌。

　　That oxygen is fundamentally toxic¹² often comes as a surprise to those of us who find it so convivial¹³ to our well-being,  氧从根本上说是很毒的，我们听了往往会大吃一惊，因为许多人觉得呼吸氧是很舒服的事，

　　but that is only because we have evolved to exploit it. 但那只是因为我们已经逐步进化到了能利用氧。

　　To other things it is a terror. 对于别的东西来说，它是一种可怕的东西。

　　It is what turns butter rancid and makes iron rust¹⁴.  它使黄油变质，使铁生锈。

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