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1、1. Greedy guts?（The Economists Jan 4th, 2007） ALTHOUGH most people prefer not to think about it, human guts are full of bacteria. And a good thing, too. These intestinal bugs help digestion, and also stop their disease-causing counterparts from invading. In return, their human hosts provide them wit
2、h a warm place to live and a share of their meals. Now it is working rather too well. A group of researchers led by Jeffrey Gordon, of the Washington University School of Medicine, in St Louis, has found that some types of microbes are a lot better than others at providing usable food to their hosts
3、. In the past, when food was scarce, those who harboured such microbes would have been blessed. These days, paradoxically, they are cursed, for the extra food seems to contribute to obesity. Dr Gordons research is outlined in a paper published in this weeks Proceedings of the National Academy of Sci
4、ences (PNAS) and two others published last month in Nature. In the Nature papers, he and his team reported that obese people have a different mix of gut microbes from that found in lean peoplea mix that is more efficient at unlocking energy from the food they consume. The researchers sequenced bacte
5、rial DNA from faecal samples taken from volunteers and discovered that those who were obese had a higher proportion of Firmicutes than lean people did.Bugs in the system This also turned out to be true in mice, and working with these rodents, the researchers discovered that the types of Firmicute fo
6、und in obese animals are more efficient at converting complex polysaccharides into simple, usable sugars such as glucose. In effect, the Firmicutes made more energy available from the same amount of food. The researchers were even able to make mice that had been raised in a germ-free environment fat
7、ter or thinner by colonising their guts with microbes from either obese or lean mice. It sounds simple enough. Unfortunately, further probing showed that the story is a little more complicated, for Dr Gordon did not merely count the gut bacteria of fat and thin peoplehe then put some of the fat ones
8、 on a diet. As these once-obese humans lost weight over the course of a year, their mix of gut microbes changed to reflect their new, svelte status. Why this happened is not clear. It does not seem to have been a result of the composition of the diet, since the effect was the same whether people los
9、t weight with a low-fat diet or a low-carbohydrate diet. Nevertheless, this part of the experiment suggests it is weight that determines gut biodiversity, not the other way round. The paper published in PNAS, though, supports the idea that the bacterial mixture is cause not effect, by adding yet ano
10、ther element to the story. In this study, Dr Gordon took normal mice and germ-free mice, and fed both groups a “Western” diet that was high in fat and sugar. The normal mice gained weight; the germ-free mice stayed lean. The findings do emphasis how profound the relationship is between people and th
11、eir gut bacteria. These bacteria can be thought of as an additional digestive organ. Alternatively, humans might view themselves as a sort of collective organisma human casing surrounding a vast colony of microbes. It is just a pity that this colony is working so hard on behalf of its casing that, i
12、n an era when food comes from the supermarket rather than the savannah, the result is rather too good. 1. By “Now it is working too well” (line 1, paragraph 2), the author implies .A. guts bacteria help digestion and prevent diseasecausing counterparts from invading B. some guts microbes work well t
13、o provide a lot of usable food to human C. the extra food provided by some guts microbes can cause heavy weight D. when food is scarce, some guts microbes can make human blessed 2. Dr Gordons research has found that . A. all guts microbes are good at providing usable food to their hosts B. Firmicute
14、s account for a higher proportion in slim people than in heavy people C. it is weight that determines ones mix of guts microbes D. the more food, the more energy Firmicutes can make available 参考译文参考译文 贪婪的肠道？贪婪的肠道？ 虽然大多数人不愿去想，但是人的肠道充满了各种细菌是个不争的事实，它们对人体 是大有裨益的，因为不仅有助于消化，还能阻止病原菌的入侵。作为回报，人类宿主为其 提供了温暖的生存
15、环境且供给营养。 但现在这种关系有点“过”了，由华盛顿大学医学院(位于路易斯)的 Jeffrey Gordon 领 导的研究小组发现，有几种微生物在为宿主供给可利用的营养时表现得异常活跃。如果过 去食物稀缺，那么带有该等微生物的人是幸运的，但换作现在他们却是不幸的，因为过多 的食物可能会导致肥胖。 Gordon 博士的研究以论文形式刊登在本周的美国国家科学院院刊上，另外两篇论 文则在上个月的自然杂志上发表。他和他的小组在自然杂志中的两篇论文中提到 肥胖与苗条人士的肠道微生物群大不相同，肥胖的人体内的微生物能更高效地将宿主摄取 食物中的能量释放出来。研究人员从志愿者粪便样本中提取细菌的 DNA，
16、对其进行测序， 而后发现肥胖人士体内壁厚菌门的微生物的比例比苗条人士要高。 消化系统内的细菌消化系统内的细菌 这一结果在小鼠实验中也得到了证实，研究人员发现肥胖小鼠体内的壁厚菌能更高效 地将复杂的多糖转化为结构简单、可利用的糖(例如葡萄糖)。食物量相等的条件下，壁厚 菌能有效地产生更多的能量。研究者甚至能使在无菌环境中培养的小鼠变胖或变瘦，这是 通过将肥胖或苗条小鼠体内的细菌注射到无菌小鼠体内实现的。 这听上去很简单，但进一步探查就会发现事实并非如此，因为 Gordon 博士并没有单 单检测肥胖和苗条人士肠道细菌的数量，还让几名肥胖人士节食。在这一年中，这些曾经 肥胖的人的体重逐渐减轻，他们的肠道微生物也发生了改变以反映其日渐苗条的身材。但 是发生这种情况的原因还不明了，并没有显示是食物构成变化导致的，因为人们无论是靠 低脂还是低碳水化合物的食谱减肥，效果都一样。这部分实验表明是体重决定了肠道细菌 的多样性，而不是肠道细菌多样
