LIFE is about choices. And one of those choices, in evolutionary terms, is about how long to live. Multicellular organisms, such as humans, are a compromise between the small number of cells that carry genes into the next generation (eggs and sperm) and the vast number that do not (all the others). For life to continue, it is essential that eggs and sperm are able to fulfil their destiny. That means keeping the rest of the body in good shape. But because organisms have limited resources, they must balance the demands of bodily repair and reproduction. The resulting compromise maximises reproduction over a lifetime at the expense of the body's gradual deterioration. Muscles weaken. Bones grow fragile. Skin creases. Nerve cells degenerate. And eventually the whole lot collapses.
生命就是各种各样的选择。以进化论而言，生物的一个选择就是要活多久。多细胞有机物，例如人类，就是少量携带基因进入下一代的细胞（精子和卵子）与大量不携带基因的细胞（所有其他的细胞）之间的折衷妥协。为使生命延续，精子和卵子能够完成使命是非常重要的，这意味着身体其它部位要保持健康。然而，由于有机体资源有限，必须均衡身体各部分修复与生殖的需要。这一妥协结果将是在一生中以身体逐渐衰老为代价而实现生长繁殖的最大化。肌肉逐渐松弛，骨骼变得脆弱，皮肤起皱纹，神经细胞退化。最终整个躯体都崩溃。
Biologists call this explanation of ageing the disposable soma theory, soma being the Greek word for “body”. Until recently, it was assumed that the theory did not apply to unicellular organisms such as bacteria, since they have no soma to dispose of, merely a single cell that creates the next generation by dividing in two. But recent discoveries have suggested that bacteria, too, face compromises between maintaining themselves and reproducing. A paper just published in the Proceedings of the National Academy of Sciences, by Milind Watve and his colleagues at Abasaheb Garware College, in Pune, India, has examined what is going on.
生物学家将这一衰老过程的解释称为“抛弃躯体论”（the disposable soma theory），soma是在希腊语中意为“躯体”。就在不久之前，人们还认为这一理论并不适用于单细胞有机物，例如细菌，因为它们没有可以抛弃的躯体，仅以单个细胞一分为二繁衍后代。然而最近的研究表明，这些细菌也面临着维护自身与繁衍后代的选择。《美国国家科学院院刊（Proceedings of the National Academy of Sciences）》刚刚发表的一篇论文检测了这一过程。该论文由就职于印度普那（Pune）阿巴萨赫布.格瓦热学院（Abasaheb Garware College ）的Milind Watve及其同事发表。
Under a microscope, bacteria appear to reproduce by dividing exactly down the middle. Instead of growing, giving rise to offspring and fading away to death, the mother cell actually becomes its two daughter cells. The assumption was that these daughters are as close to identical as random variation permits, and that neither is subject to the sort of ageing imposed by the disposable soma theory. But that assumption depended on another: that the components of the mother cell are dealt out equally to the two daughters. Examination of bacterial division using modern techniques has shown that this is not always so. Sometimes one daughter gets preferential treatment, by receiving newly synthesised components instead of old, battered and repaired ones. The more aged a bacterium's innards are, the more mortal it appears. It is slower to metabolise and likelier to die before it has reproduced.
在显微镜下，细菌似乎从正中间一分为二进行繁殖。母细胞并没有继续成长、养育子细胞并衰老至死，而是形成了两个子细胞。人们对此的假设是这些子细胞在随机变化范围内尽可能地相似。且这两个子细胞都不受到那套“抛弃躯体论”所带来的衰老过程的影响。然而这一假设的成立还有赖于另一个假设的成立：母细胞的成分被均等地分为两个子细胞。使用现代技术对细胞分裂进行检测所的结果表明情况并非如此。其中一个子细胞得到较好的待遇，获得了新合成的细胞成分，而不是那些老旧的、破损的、修补的细胞成分。细菌内部成分越衰老，它就越接近死亡。他的新陈代谢过程减缓，更有可能在繁殖之前死亡。
Dr Watve asked himself why this should be, and constructed a theoretical world inside a computer to investigate the matter. In this world, a bacterium can “choose” a mortal strategy, dumping all its old components into one daughter with limited prospects, and betting most of its future—and all of its new bits—on the other. Alternatively, it can divide itself symmetrically. The latter choice brings, if not eternal youth, then an equal pressure to avoid ageing, since neither daughter is more prone to death than the mother had been. But these daughters grow more slowly than the favoured daughters of unequal divisions, because their resources have to be divided between maintenance and reproduction.
Watve博士追问自己这一现象的原因，并用计算机建造了一个理论世界来进行研究。在这一理论世界中，一个细菌能够“选择”死亡策略，它可以将所有老旧的细胞成分分配给一个没有前景的子细胞，并将所有希望寄托在另一个子细胞上，并将新细胞成分分配给它。或者，这个细菌能够将自己对称分配。后一种选择中的两个子细胞，如果不能永葆青春，那么也有同等机会避免衰老，因为这两个子细胞都不会比母细胞更容易衰老。不过这两个子细胞比不对称分配策略下受惠的子细胞的生长速度要慢，因为它们的资源不得不在维护自身和繁殖后代中进行分配。
When Dr Watve ran the model, he discovered that the main determinant of whether symmetrical or asymmetrical division was favoured was the amount of food around. In impoverished environments (in the real world, that might include lakes and oceans), the slower-growing daughters of symmetrical divisions had the upper hand because they used what little resources were available more efficiently. That was because the runts tended to die before they could reproduce, thus wasting the food that they had already eaten. In richer places, fewer runts died, and the daughters with shiny, new bits grew and divided very rapidly indeed. And that fits with the finding that bacteria inside the nutrient-rich human gut grow rapidly and in an asymmetrical manner.
当Watve博士运行这一模型，他发现细胞分裂究竟是否对称分割取决于其周围的食物量。在贫瘠的环境中（现实世界中，可能包括湖泊或海洋），平均分割的增长缓慢的子细胞可能更占优势，因为它们能更有效地利用有限的资源。这是因为那些非对称分个所得子细胞中的弱者有可能在繁殖之前就死亡，这样就浪费了他们所吸收的食物。而在富足的环境中，那些较弱的子细胞死得较少，那些拥有新细胞成分的子细胞生长、分割的更迅速。而这与人们的发现相吻合：在养分充足的人体内脏中，细菌生长得更快，且以非对称形式分割。
Cosseted laboratory bacteria also divide asymmetrically, again in conformity with the theory. The question is whether those in poorer environments will prove more egalitarian. And the answer? No one has yet looked.
实验室中养分充足的细菌也是非对称的分割，再次证实了这一理论。问题是，是否能证明那些在贫瘠环境中的细胞更倾向于对称分割？对此问题还无人能回答。
你可以使用这个链接引用该篇文章 http://publishblog.blogchina.com/blog/tb.b?diaryID=6274264