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本文摘译自最新一期的“经济学家”杂志-Economist

People are not just people. They are an awful lot of microbes, too 人类不光是我们自身那么简单,还是各种各样令人恐惧的微生物组合体

Aug 18th 2012 | from the print edition

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POLITICAL revolutionaries turn the world upside down. Scientific ones more often turn it inside out. And that, almost literally, is happening to the idea of what, biologically speaking, a human being is.

政治变革将整个世界颠覆,而科学变革通常从里到外地将这个世界揭示得一览无疑,从生物学角度考虑变革会使我们产生一种想法那就是人类到底是什么?有时提出这一问题还颇据文学色彩。

 

 The traditional view is that a human body is a collection of 10 trillion cells which are themselves the products of 23,000 genes. If the revolutionaries are correct, these numbers radically underestimate the truth. For in the nooks and crannies of every human being, and especially in his or her guts, dwells the microbiome: 100 trillion bacteria of several hundred species bearing 3m non-human genes. The biological Robespierres believe these should count, too; that humans are not single organisms, but superorganisms made up of lots of smaller organisms working together.

我们以往的传统观念是人类身体本身由10万亿个细胞组成,而这些细胞自身又是由2.3万个基因连接在一起。如果变革派们的观点是正确的话,恐怕实际数字还要高。对于人类身体内各个角落而言,特别是内脏部分都匿藏着微生物,数量高达100万亿,品种各异有数百之多,而这些品种都同3百万非人类基因有关。生物学家罗博斯贝尔确信这些数字的确也是可以计算的。人类不单纯是各种生物体的融合,同时也是由相互作用更微小超级生物体所组成。

 

It might sound perverse to claim bacterial cells and genes as part of the body, but the revolutionary case is a good one. For the bugs are neither parasites nor passengers. They are, rather, fully paid-up members of  a community of which the human “host” is but a single (if dominating) member. This view is increasingly popular: the world’s leading scientific journals, Nature and Science, have both reviewed it extensively in recent months. It is also important: it will help the science and practice of medicine.

宣称微生物细胞和基因作为我们身体的一部分似乎有些非同寻常,可下面这个变革案例就是一个很好的例证。比如说:这些小虫既不是寄生虫也不是过客。相反他们是以人类为主体所组成的群体中效犬马之劳的成员,而人类只不过是其中一个单一份子(虽然是起主导地位的)。这一观点日趋普遍化。世界最为权威的科学杂志“自然与科学”在近几个月里也深入地探讨了这个问题,因为这有助于科学和医学实践,对我们来说同样显得尤为重要。

 

All in this together  一切都是融合的

 

The microbiome does many jobs in exchange for the raw materials and shelter its host provides. One is to feed people more than 10% of their daily calories. These are derived from plant carbohydrates that human enzymes are unable to break down. And not just plant carbohydrates. Mother’s milk contains carbohydrates called glycans which human enzymes cannot digest, but bacterial ones can.

作为换取人类主体所提供的原材料和避风港,微生物要做很多事。最为突出的就是为人类提供每日所需总热量的10%,且都来自于人类酶所无法化解的植物碳水化合物。不仅仅是植物碳水化合物。母亲的奶中就含有被称为“胶原”的物质据说人类是无法消化的酶,可微生物却能将这种物质消化掉。

 

This alone shows how closely host and microbiome have co-evolved over the years. But digestion is not the only nutritional service provided. The microbiome also makes vitamins, notably B2, B12 and folic acid. It is, moreover, capable of adjusting its output to its host’s needs and diet. The microbiomes of babies make more folic acid than do those of adults. And microbiomes in vitamin-hungry places like Malawi and rural Venezuela turn out more of these chemicals than do those in the guts of North Americans.

仅这方面就可以表明人类同微生物相伴进化很多年。可消化并不只是供给营养。微生物还制造维他命,像众所周知的B2,B12和叶酸。而且还可以根据人类所需和膳食的情况调节这些维生素的产出量。儿童身体中所具有的微生物所产出的叶酸要比成年人多,且像马拉维和委内瑞拉这些缺乏维生素的地区,当地人身体中的微生物在制造这些化学物质方面比北美地区人要更多。

 

The microbiome also maintains the host’s health by keeping hostile interlopers at bay. An alien bug that causes diarrhoea, for instance, is as much an enemy of the microbiome as of the host. Both have an interest in zapping it. And both contribute to the task. Host and microbiome, then, are allies. But there is more to it than that. For the latest research shows their physiologies are linked in ways which make the idea of a human superorganism more than just a rhetorical flourish.

微生物还可以通过困住有害细菌的入侵以保持人类身体健康。一只可以引起人腹泻的外来昆虫是微生物的天敌同时也是人类的天敌,且两者都会有意诛之,它们的目标是一致的。人类和微生物联手同盟。而现在看来还有更深层含义。最新研究表明生物学在诸多方面都同创造人类超级生物体理念有千丝万缕的联系,绝不只是一种华丽言辞的表述。

 

These links are most visible when they go wrong. A disrupted microbiome has been associated with a lengthening list of problems: obesity and its opposite, malnutrition; diabetes (both type-1 and type-2); atherosclerosis and heart disease; multiple sclerosis; asthma and eczema; liver disease; numerous diseases of the intestines, including bowel cancer; and autism. The details are often obscure, but in some cases it looks as if bugs are making molecules that help regulate the activities of human cells. If these signals go wrong, disease is the consequence. This matters because it suggests doctors have been looking in the wrong place for explanations of these diseases. It also suggests a whole new avenue for treatment. If an upset microbiome causes illness, settling it down might effect a cure.

当它们出现问题时这种联系才愈显突出。一个受到干扰的微生物显然同人类所遇到的各种纷繁健康问题密切相关,如:肥胖症和消瘦症,缺乏营养,糖尿病(一型和二型),动脉粥样硬化,心脏疾病,多发性硬化,哮喘以及湿疹; 肝脏疾病,各种肠道疾病包括直肠癌以及自闭症。这其中的详情令人费解,不过有些案例看起来是昆虫制造出分子来帮助规范人类细胞的活动。如果信号出错,疾病就会接踵而来。的确应该当回事因为这说明医生们在寻求解释这些疾病原因方面一直是在步入误区。同时还为治疗这些疾病开辟了一条新途径。假如被扰乱了的微生物是导致人类疾病直接原因的话,那么要是能让这些紊乱的微生物平静下来或许就能有效的医治那些疾病。

 

Yogurt companies and health-food fanatics have been banging this drum for years. And in the case of at least one malady, irritable-bowel syndrome, they are right. So-called probiotics, a mixture of about half a dozen bacterial species found in yogurt, do act to calm this condition. But there is little evidence that consuming probiotics has the tonic effect on healthy people that certain adverts suggest.

酸奶生产公司和那些奉行健康食品的狂热崇拜者们多年来一直为此擂鼓呐喊,起码在肠道紊乱综合症方面他们的这种做法是对的。所谓益生菌在酸奶中能找到6种混合菌目的是要调整紊乱的肠道。可目前还没有证据表明食用益生菌对健康人体有令人振奋的作用,起码没有像广告上吹的那么神。

 

A handful of doctors are taking a more fundamental approach to another microbiome-related disease, infection with Clostridium difficile. This bacterium, which causes life-threatening distension of the gut in some people who have been treated with antibiotics and thus had their microbiomes disrupted, is a bane of hospitals. It kills 14,000 people a year in America alone. But recent experiments have shown it can be eliminated by introducing, as an enema, the faeces of a healthy individual. “Stool transplants” are a pretty crude approach, to be sure, but the crucial point is that microbes are much easier to manipulate than human cells. For all the talk of superorganisms (and despite the yuck factor of what is being moved from one body to another), transplanting a microbiome is far easier than transplanting a heart or a kidney.

有些医生正在寻求一种更有效的方法来治疗与微生物有关的疾病,这种疾病是被顽固的棱菌感染。在那些长期接受抗生素治疗的人们肠道内引发致命的肠扩张从而使肠道内的微生物体紊乱,这种杆菌可以给医院带来灾难。每年单美国就因此造成1.4万人死亡。最近试验表明可以通过采用健康人体排泄的粪便研制一种灌肠剂就能将这些顽固有害杆菌彻底消灭掉。所谓”粪便移植“相对方法原始但的确可靠,可问题的关键在于摆弄微生物比左右人类细胞更容易。尽管所有谈论超有机体即从一个人的身体转到另一个人的身体中感觉上有点儿恶心,可移植微生物要比移植一颗心脏和肾脏来得更为容易。

 

Disgusting but useful 看似令人恶心但的确有用

Two other areas look promising. One is more sophisticated deployment of the humble antibiotic, arguably the pharma industry’s most effective invention. At the moment antibiotics are used mainly to kill infections. In the future they might have a more subtle use—to manipulate the mix of bugs within a human, so that good bugs spread at the expense of bad ones.

有两个领域颇有前景。一是更加精细的部署常规抗生素,抗生素号称是医药工业最有效的发明,但却颇有争议。目前抗生素主要用在治疗感染方面。将来抗生素会更有妙用即:在人身体内释放虫药混合体将坏虫杀死。

 

The other field that may be changed is genetics. Many of the diseases in which the microbiome is implicated seem to run in families. In some, such as heart disease, that is partly explained by known human genes. In a lot, though, most notably autism, the genetic link is obscure. This may be because geneticists have been looking at the wrong set of genes—the 23,000 rather than the 3m. For those 3m are still inherited. They are largely picked up from your mother during the messy process of birth. Though no clear example is yet known, it is possible that particular disease-inducing strains are being passed down the generations in this way.

另外或许会改变的领域是遗传学。许多由微生物引发的疾病中有相当一部分都是在家族内传播的。有些如心脏病可以部分地解释为人类基因所致。还有最为显著的自闭症其中有很多引发原因都是同遗传有关,但这种关联至今还不清楚。或许是遗传学家们一直以来所寻求的基因组出了问题,应该是2.3万人类基因而非3百万非人类基因。因为3百万非人类仍然是可遗传的。在令人手忙脚乱的接生过程中这些基因大多是从母亲那里筛选来的。尽管明确的原因还不清楚,但特殊的疾病如:幽门杆菌类疾病都是通过生育传给下一代的。

 

As with all such upheavals, it is unclear where the microbiome revolution will end up. Doctors and biologists may truly come to think of people as superorganisms. Then again, they may not. What is clear, though, is that turning thinking inside out in this way is yielding new insights into seemingly intractable medical problems, and there is a good chance cures will follow. Vive la révolution!

就如上阐述的所有剧变而言,这场微生物变革将会到哪儿才是个头呢?目前还尚不清楚。医生和生物学家们或许真正要思考的应该是作为超级生物体的人类本身。然而再次说明的是他们或许没有这样去考虑。有一点是清楚的那就是采用从里到外的思考方式似乎会对令人棘手的医学问题产生新的深刻认识,而接下来就会有机会找到治愈方法。要我说应该是“变革万岁”

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