物以類聚，人以菌分

　　Date： Friday， 22 Apr 2011 03：32

　　原作者：

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

　　譯者Loco

　　科學(xué)家表示，細菌將人類分為三種

　　在20世紀(jì)初，科學(xué)家發(fā)現(xiàn)人類的血液類型可分為四種，每個人必屬其中之一。如今科學(xué)家又發(fā)現(xiàn)了一種給人分類的方法：細菌。每個人體內(nèi)都有成千上萬種不同的細菌，然而最近一個科學(xué)家小組宣布，在他們研究的人群里，有三種截然不同的生態(tài)環(huán)境存在于消化道中。

　　“這是一個重要的進步。這是我們首次發(fā)現(xiàn)人類消化道的生態(tài)環(huán)境可以劃分為不同的類別。”

　　來自德國海德堡“歐洲分子生物學(xué)實驗室”的Peer Bork是研究小組的頭。該小組發(fā)現(xiàn)在他們所謂的“腸道類型”和他們研究對象（包括歐洲人、美國人和日本人）的種族背景之間沒有任何聯(lián)系。

　　同時，“腸道類型”和性別、體重、健康狀況、年齡也沒有任何聯(lián)系。他們正在著手研究這一現(xiàn)象背后的原因。有一種可能，即不同種類的細菌在嬰兒消化道中建立的早期種群完全是隨機進行的。

　　這些細菌改變了消化道，使得其后只有特定種類的細菌才能存活其中。

　　無論是何種原因造成了不同的“腸道類型”，其最終結(jié)果就是人類健康狀況因此受到不同的影響。消化道細菌參與食物的消化并合成維生素，其使用的酶是人體細胞無法分泌的。

　　Bork博士及其同事發(fā)現(xiàn)，不同“腸道類型”產(chǎn)生的酶有所不同。甲類腸道產(chǎn)生更多的酶用于生成維生素B7（或稱維生素H），而乙類腸道則有更多生成維生素B1（硫胺素）的酶。

　　將血液分為A型、B型、AB型及O型對醫(yī)生行醫(yī)產(chǎn)生重大影響。只要輸血者和被輸血者的血液類型相互吻合，輸入患者體內(nèi)的血液受到排斥的可能性就大大降低了。同樣，“腸道類型”的發(fā)現(xiàn)將來也可能在醫(yī)藥領(lǐng)域獲得應(yīng)用，而且產(chǎn)生更為深遠的影響。

　　Bork博士說‘腸道類型’的實用價值現(xiàn)在就很明顯了，比方說，醫(yī)生可以根據(jù)病人的“腸道類型”有針對性地開具處方或食譜；醫(yī)生甚至還可以根據(jù)腸道類型找到抗生素的替代品，因為后者如今正在逐漸失去效力。醫(yī)生可以不再想方設(shè)法去殺死那些導(dǎo)致腸道生態(tài)環(huán)境失衡的致病細菌，而是幫助有益的細菌恢復(fù)到正常的狀態(tài)。

　　Bork博士表示還需要進行更多的實驗。研究人員還需要針對諸如非洲人、中國人等其他人種進行腸道類型的研究。他還表示，由于迄今為止所有研究對象都來自發(fā)達國家，他們吃的東西都差不多，因此這是一個缺陷。“我們沒有來自遙遠山村的研究對象”。

　　“腸道類型”的發(fā)現(xiàn)源于對人體細菌種類（即所謂的腸道微生物組）的常年研究——這是一項極其艱巨的任務(wù)，因為每個人體內(nèi)都有近100兆個細菌（要知道人體自身的細胞數(shù)量也不過10兆）。但是科學(xué)家無法在實驗室中培育這些細菌，從而對其進行區(qū)分并了解其特性。

　　隨著基因技術(shù)的進步，科學(xué)家知道了如何通過分析細菌的DNA對細菌進行研究。通過從人體皮膚、唾液和糞便中提取DN***段，科學(xué)家從而將細菌DNA和人體的DNA區(qū)分開來。他們在細菌的DNA中尋找特定基因的不同變種，并將其與已知細菌種類進行比較。有時，這些變種來自于一些常見的細菌，比如E. coli.而有時，這些基因?qū)儆谌�新的種類。

　　這些研究讓人們看到了如同熱帶雨林中的生物多樣性那樣豐富的細菌種類。身體的不同部位有不同的細菌種類。同時，科學(xué)家在人類個體身上發(fā)現(xiàn)了極大的不同。比方說，某人口里生活的許多細菌，在其他人嘴里就沒有。

　　科學(xué)家猜測，對細菌進行更加深入的研究可能揭示出人體腸道微生物組具有的統(tǒng)一性。在過去的幾年里，研究人員已經(jīng)確認(rèn)了人體內(nèi)成百上千種細菌的基因組，即基因的完整結(jié)構(gòu)�，F(xiàn)在，他們可以將這些基因組作為參考，與人體內(nèi)的其他細菌進行基因進行比對。

　　科學(xué)家可以確認(rèn)這些基因的功能，并確認(rèn)這些細菌屬于何種類型。通過統(tǒng)計找到的基因，科學(xué)家還可估算出各種細菌的相對數(shù)量。

　　在最近的一次試驗中，22個實驗對象分別來自于丹麥、法國、意大利和西班牙。Bork博士和他的小組對他們腸道內(nèi)的細菌進行了分析。這些人有的健康，有的人過于肥胖，而有的人則患有像孔羅氏病這樣的腸道疾病。研究人員根據(jù)1511種細菌的基因組尋找DN***段，并將其試驗結(jié)果與之前在13個日本人和4個美國人身上進行的試驗結(jié)果合并。

　　接下來，科學(xué)家在其中尋找規(guī)律。“我們不做任何假設(shè)，因此任何發(fā)現(xiàn)都是新的”。

　　然而，Bork博士還是為研究結(jié)果感到震驚，因為所有基因組可以被完美地劃分為三個類型。

　　不僅如此，根據(jù)Bork博士及其同事周三在《自然》雜志上的報道，不同的“腸道類型”由不同類別的細菌種類組成。比方說，甲類腸道有較多的Bacteroides細菌，而乙類腸道中Bacteroides的含量則較少，而Prevotella類的細菌則異常豐富。

　　“無論怎樣對數(shù)據(jù)進行刪減，這三種腸道類型始終存在”。

　　Bork博士及其同事已在其他的腸道微生物組調(diào)查中發(fā)現(xiàn)了這三種腸道類型的存在。而且他們的研究對象已經(jīng)達到了400人之多，這種分類始終都存在。

　　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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