(单词翻译:单击)
From caesarean sections to chemotherapy, antibiotics make much of modern medicine possible by keeping bacterial infections at bay.
从剖腹产到化疗，抗生素通过防止细菌感染使现代医学的大部分疗法成为可能。
That is why the growing bacterial resistance to those drugs is so worrying.
这也是越来越多细菌对抗生素的耐药性令人愈发担忧的原因。
The United Nations estimates that by 2050 infections with drug-proof bacteria could claim up to 10m lives a year, more than double the current toll.
联合国估计，到2050年，每年的耐药细菌感染将夺去多达1000万人的生命，是目前死亡人数的两倍多。
A problem with tackling such resistance is that scientists have an incomplete sense of how it arises.
对付这种抗药性还存在一个问题，科学家还没有完全了解它是如何产生的。
One way is essentially random: a chance mutation in a particular bacterium may make a certain drug less lethal.
有一种基本上可以说是随机的情况:一种特定细菌的偶然突变可能会降低某种药物的致命性。
If that bacterium survives a dose of treatment, its descendants will inherit that same resistance.
如果这种细菌在一定剂量的治疗中存活下来，它的后代将继承同样的抵抗力。
But the speed at which bacterial drug resistance spreads means that cannot be the whole story.
但是细菌耐药性传播的速度意味着这并不是全部的“故事”。
“I always felt there were additional mechanisms of evolution.
“我一直觉得还有其他的进化机制。
And probably more powerful ones,” says John Chen at the National University of Singapore.
而且可能更强大，”新加坡国立大学的约翰·陈说。
In a paper in Cell, Dr Chen and his colleagues identify one such mechanism.
在《细胞》杂志的一篇论文中，陈博士和他的同事们发现了这样的一种机制。
It centres not on the bacteria themselves, nor the viruses that are known to infect them, but on yet more rudimentary genetic parasites that exploit these viruses in turn.
它的重点不是细菌本身，也不是已知的感染它们的病毒，而是更为基本的遗传寄生物，它们会依次利用这些病毒。
The fact that bacteria can transfer genes horizontally, to other unrelated bugs, as well as vertically to their offspring, is well known.
众所周知，细菌可以将基因水平传递给其他不相关的细菌，也可以垂直传递给它们的后代。
Some are exchanged via small loops of DNA called plasmids.
一些基因会通过被称为质粒的DNA小环交换。
Others are transmitted by bacteriophages, specialised viruses that infect bacteria.
另一些则通过噬菌体传播，噬菌体是一种专门感染细菌的病毒。
When a phage latches on to a bacterium, its DNA forces the bacterium to make more copies of the virus until it bursts.
当噬菌体附着在细菌上时，它的DNA迫使细菌复制更多的病毒，直到它破裂。
Sometimes, small fragments of bacterial DNA can be erroneously included with the new viruses.
有时，细菌DNA的小片段可能被错误地包含在新病毒中。
If they infect another bacterium, the hitchhiking DNA can end up integrated into the new host’s genome.
如果它们感染了另一种细菌，搭便车的DNA最终会整合到新宿主的基因组中。
