物以类聚，人以菌分

　　Date： Friday， 22 Apr 2011 03：32

　　原作者：

　　来源Gut Bacteria Divide People Into 3 Types， Scientists Report - NYTimescom

　　译者Loco

　　科学家表示，细菌将人类分为三种

　　在20世纪初，科学家发现人类的血液类型可分为四种，每个人必属其中之一。如今科学家又发现了一种给人分类的方法：细菌。每个人体内都有成千上万种不同的细菌，然而最近一个科学家小组宣布，在他们研究的人群里，有三种截然不同的生态环境存在于消化道中。

　　“这是一个重要的进步。这是我们首次发现人类消化道的生态环境可以划分为不同的类别。”

　　来自德国海德堡“欧洲分子生物学实验室”的Peer Bork是研究小组的头。该小组发现在他们所谓的“肠道类型”和他们研究对象（包括欧洲人、美国人和日本人）的种族背景之间没有任何联系。

　　同时，“肠道类型”和性别、体重、健康状况、年龄也没有任何联系。他们正在着手研究这一现象背后的原因。有一种可能，即不同种类的细菌在婴儿消化道中建立的早期种群完全是随机进行的。

　　这些细菌改变了消化道，使得其后只有特定种类的细菌才能存活其中。

　　无论是何种原因造成了不同的“肠道类型”，其最终结果就是人类健康状况因此受到不同的影响。消化道细菌参与食物的消化并合成维生素，其使用的酶是人体细胞无法分泌的。

　　Bork博士及其同事发现，不同“肠道类型”产生的酶有所不同。甲类肠道产生更多的酶用于生成维生素B7（或称维生素H），而乙类肠道则有更多生成维生素B1（硫胺素）的酶。

　　将血液分为A型、B型、AB型及O型对医生行医产生重大影响。只要输血者和被输血者的血液类型相互吻合，输入患者体内的血液受到排斥的可能性就大大降低了。同样，“肠道类型”的发现将来也可能在医药领域获得应用，而且产生更为深远的影响。

　　Bork博士说‘肠道类型’的实用价值现在就很明显了，比方说，医生可以根据病人的“肠道类型”有针对性地开具处方或食谱；医生甚至还可以根据肠道类型找到抗生素的替代品，因为后者如今正在逐渐失去效力。医生可以不再想方设法去杀死那些导致肠道生态环境失衡的致病细菌，而是帮助有益的细菌恢复到正常的状态。

　　Bork博士表示还需要进行更多的实验。研究人员还需要针对诸如非洲人、中国人等其他人种进行肠道类型的研究。他还表示，由于迄今为止所有研究对象都来自发达国家，他们吃的东西都差不多，因此这是一个缺陷。“我们没有来自遥远山村的研究对象”。

　　“肠道类型”的发现源于对人体细菌种类（即所谓的肠道微生物组）的常年研究——这是一项极其艰巨的任务，因为每个人体内都有近100兆个细菌（要知道人体自身的细胞数量也不过10兆）。但是科学家无法在实验室中培育这些细菌，从而对其进行区分并了解其特性。

　　随着基因技术的进步，科学家知道了如何通过分析细菌的DNA对细菌进行研究。通过从人体皮肤、唾液和粪便中提取DN***段，科学家从而将细菌DNA和人体的DNA区分开来。他们在细菌的DNA中寻找特定基因的不同变种，并将其与已知细菌种类进行比较。有时，这些变种来自于一些常见的细菌，比如E. coli.而有时，这些基因属于全新的种类。

　　这些研究让人们看到了如同热带雨林中的生物多样性那样丰富的细菌种类。身体的不同部位有不同的细菌种类。同时，科学家在人类个体身上发现了极大的不同。比方说，某人口里生活的许多细菌，在其他人嘴里就没有。

　　科学家猜测，对细菌进行更加深入的研究可能揭示出人体肠道微生物组具有的统一性。在过去的几年里，研究人员已经确认了人体内成百上千种细菌的基因组，即基因的完整结构。现在，他们可以将这些基因组作为参考，与人体内的其他细菌进行基因进行比对。

　　科学家可以确认这些基因的功能，并确认这些细菌属于何种类型。通过统计找到的基因，科学家还可估算出各种细菌的相对数量。

　　在最近的一次试验中，22个实验对象分别来自于丹麦、法国、意大利和西班牙。Bork博士和他的小组对他们肠道内的细菌进行了分析。这些人有的健康，有的人过于肥胖，而有的人则患有像孔罗氏病这样的肠道疾病。研究人员根据1511种细菌的基因组寻找DN***段，并将其试验结果与之前在13个日本人和4个美国人身上进行的试验结果合并。

　　接下来，科学家在其中寻找规律。“我们不做任何假设，因此任何发现都是新的”。

　　然而，Bork博士还是为研究结果感到震惊，因为所有基因组可以被完美地划分为三个类型。

　　不仅如此，根据Bork博士及其同事周三在《自然》杂志上的报道，不同的“肠道类型”由不同类别的细菌种类组成。比方说，甲类肠道有较多的Bacteroides细菌，而乙类肠道中Bacteroides的含量则较少，而Prevotella类的细菌则异常丰富。

　　“无论怎样对数据进行删减，这三种肠道类型始终存在”。

　　Bork博士及其同事已在其他的肠道微生物组调查中发现了这三种肠道类型的存在。而且他们的研究对象已经达到了400人之多，这种分类始终都存在。

　　附英文原文：

　　New York Times - Science

　　Bacteria Divide People Into 3 Types， Scientists Say

　　By CARL ZIMMER， Published： April 20， 2011

　　In the early 1900s， scientists discovered that each person belonged to one of four blood types. Now they have discovered a new way to classify humanity： by bacteria. Each human being is host to thousands of different species of microbes. Yet a group of scientists now report just three distinct ecosystems in the guts of people they have studied.

　　Blood type， meet bug type.

　　“It‘s an important advance，” said Rob Knight， a biologist at the University of Colorado， who was not involved in the research. “It’s the first indication that human gut ecosystems may fall into distinct types.”

　　The researchers， led by Peer Bork of the European Molecular Biology Laboratory in Heidelberg， Germany， found no link between what they called enterotypes and the ethnic background of the European， American and Japanese subjects they studied.

　　Nor could they find a connection to sex， weight， health or age. They are now exploring other explanations. One possibility is that the guts， or intestines， of infants are randomly colonized by different pioneering species of microbes.

　　The microbes alter the gut so that only certain species can follow them.

　　Whatever the cause of the different enterotypes， they may end up having discrete effects on people‘s health. Gut microbes aid in food digestion and synthesize vitamins， using enzymes our own cells cannot make.

　　Dr. Bork and his colleagues have found that each of the types makes a unique balance of these enzymes. Enterotype 1 produces more enzymes for making vitamin B7 （also known as biotin）， for example， and Enterotype 2 more enzymes for vitamin B1 （thiamine）。

　　The discovery of the blood types A， B， AB and O had a major effect on how doctors practice medicine. They could limit the chances that a patient‘s body would reject a blood transfusion by making sure the donated blood was of a matching type. The discovery of enterotypes could someday lead to medical applications of its own， but they would be far down the road.

　　“Some things are pretty obvious already，” Dr. Bork said. Doctors might be able to tailor diets or drug prescriptions to suit people‘s enterotypes， for example.

　　Or， he speculated， doctors might be able to use enterotypes to find alternatives toantibiotics， which are becoming increasingly ineffective. Instead of trying to wipe out disease-causing bacteria that have disrupted the ecological balance of the gut， they could try to provide reinforcements for the good bacteria. “You‘d try to restore the type you had before，” he said.

　　Dr. Bork notes that more testing is necessary. Researchers will need to search for enterotypes in people from African， Chinese and other ethnic origins. He also notes that so far， all the subjects come from industrial nations， and thus eat similar foods. “This is a shortcoming，” he said. “We don‘t have remote villages.”

　　The discovery of enterotypes follows on years of work mapping the diversity of microbes in the human body — the human microbiome， as it is known. The difficulty of the task has been staggering. Each person shelters about 100 trillion microbes.

　　（For comparison， the human body is made up of only around 10 trillion cells.） But scientists cannot rear a vast majority of these bacteria in their labs to identify them and learn their characteristics.

　　As genetics developed， scientists learned how to study the microbiome by analyzing its DNA. Scientists extracted DNA fragments from people‘s skin， saliva and stool. They learned how to recognize and discard human DNA， so that they were left with genes from the microbiome. They searched through the remaining DNA for all the variants of a specific gene and compared them with known species. In some cases， the variants proved to be from familiar bacteria， like E. coli. In other cases， the gene belonged to a species new to science.

　　These studies offered glimpses of a diversity akin to a rain forest‘s. Different regions of the body were home to different combinations of species. From one person to another， scientists found more tremendous variety. Many of the species that lived in one person’s mouth， for example， were missing from another‘s.

　　Scientists wondered if deeper studies would reveal a unity to human microbiomes. Over the past few years， researchers have identified the genomes — the complete catalog of genes — of hundreds of microbe species that live in humans. Now they can compare any gene they find with these reference genomes.

　　They can identify the gene‘s function， and identify which genus of bacteria the microbe belongs to. And by tallying all the genes they find， the scientists can estimate how abundant each type of bacteria is.

　　In the recent work， Dr. Bork and his team carried out an analysis of the gut microbes in 22 people from Denmark， France， Italy and Spain. Some of their subjects were healthy， while others were obese or suffered from intestinal disorders like Crohn‘s disease. Dr. Bork and his colleagues searched for fragments of DNA corresponding to the genomes of 1，511 different species of bacteria. The researchers combined their results with previous studies of 13 Japanese individuals and 4 Americans.

　　The scientists then searched for patterns. “We didn‘t have any hypothesis，” Dr. Bork said. “Anything that came out would be new.”

　　Still， Dr. Bork was startled by the result of the study： all the microbiomes fell neatly into three distinct groups.

　　And， as Dr. Bork and his colleagues reported on Wednesday in the journal Nature， each of the three enterotypes was composed of a different balance of species. People with type 1， for example， had high levels of bacteria called Bacteroides. In type 2， on the other hand， Bacteroides were relatively rare， while the genus Prevotella was unusually common.

　　“You can cut the data in lots of different ways， and you still get these three clusters，” Dr. Bork said.

　　Dr. Bork and his colleagues found confirmation of the three enterotypes when they turned to other microbiome surveys， and the groups continue to hold up now that they have expanded their own study to 400 people.

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