2017 考博英语 阅读题源经济学人文章每日精析（六十九）

考博英语阅读大部分博士研究生招生院校都使用《经济学人》杂志文章作为题源，考博信息网|http://www.kaoboinfo.com教育考博频道为考博生们将其中的文章进行深度分析，希望能提高大家的考博英语阅读水平，读懂长难句。

The story of yeast酵母的故事

Domesticated tipple酿酒

In a piece of genetic archaeology, researchers discover the origins of a good pin

t研究人员于基因片段中，发现了好酒的起源

Sep 10th 2016 | From the print edition 2016年9月10日 | 摘自印刷版

CATTLE ranchers know that if they want to increase their yields it is best to breed their largest cows with their biggest bulls. The same idea works when trying to improve other livestock, crops and pets. Although less well known, microorganisms can also be bred selectively. Given that yeasts have a long history of being used to ferment food and drink, archaeologists have argued for years that early craftsmen may have selectively bred yeaststrains without even realising it.养牛的大农场主都知道，要想提高牛场的产出，最好的方法就是养大量的奶牛和强壮的公牛。养家禽，种地和养宠物都是这样的道理。尽管大多数人并不知道，但是微生物也是可以拿来培育的。鉴于很早以前人们就用酵母来发酵食物，酿酒，所以考古学家已经争论了多年，他们认为早期的手工师傅们在无意识的情况下已经在有选择性的培育酵母品种了。

Microorganism：n. [微] 微生物 Ferment：vt. 使发酵argue for：赞成;支持;论证strain：种类

Now there is evidence to support this idea. Steven Maere of the University of Ghent and Kevin Verstrepen of the University of Leuven, both in Belgium, and their colleagues have been studying the genomes of culinary yeast species. As they report in Cell this week, the researchers have found evidence that people started domesticating yeast strains, particularly those used in beer, some 500 years ago.而今，有证据表明这个说法是对的。来自比利时他跟特大学的Seteven Maere和鲁汶大学的Kevin Verstrepen以及他们的同事们正在对烹调菌种基因组进行研究。他们上周在《细胞》杂志上发表了自己的文章，文中说到研究人员已经找了证据，证明大约500年前，人们已经开始人工培育酵母了——特别是那些用于酿造啤酒中的酵母。

genome：n. [遗] 基因组culinary：adj. 厨房的;烹调用的

注：《细胞》是由美国爱思维尔(Elsevier)出版公司旗下的细胞出版社(Cell Press)发行的关于生命科学领域中最新研究发现的的杂志

Today’s bakers, vintners and brewers have intimate knowledge of yeasts and choose strains that improve their products and grant specific flavours. But until the work of Louis Pasteur in the mid-19th century nobody knew that microorganisms existed. However, a process called “backslopping”, whereby part of an old successful mix of fermented dough, wine or beer is seeded into a new mix, might have allowed early yeast users to confine species that had favourable characteristics in man-made environments for years on end, effectively domesticating them. Drs Maere and Verstrepen suspected that regular backslopping would have resulted in yeasts developing traits that led them to thrive in environments managed by humans, but to struggle in the wild. To explore that idea, they set up an experiment.如今的面包师、葡萄酒商和酿酒者已经非常了解酵母了，和如何选择菌种以便提高产量并且赋予产品特殊的香味。不过直至19世纪中期Louis Pasteur的研究出现之前，无人知道微生物的存在。然而早期酵母使用者可以通过将一部分先前成功发酵的面团放入用来发酵葡萄酒或者啤酒原料里的方法，对性能良好的菌种进行控制，并且长年累月成功地培育它们。这个过程称为“接面”(注：这里只是方言，网上查不到“back-slopping”的中文意思)Maere博士和Verstrepen博士猜想，定期接面使得酵母某些特性得以发展。这些特性使得酵母在人类可控的环境中可以大量地繁殖，却在野生的环境下难以生存。为了对这一猜想进行调查，他们开始了一项实验。 Vintner：n. 葡萄酒商 Brewer：n. 酿酒者 have intimate knowledge of：非常熟悉;了解得清楚 dough：n. 生面团

注：back-slopping：就是把老酵或先前发酵过的原料，掺到需要发酵的新原料中。各地的叫法不同，请自行脑补。

Working with a team of experts from White Labs, a company in San Diego that develops and sells yeasts, the researchers analysed the genomes of 157 strains of Saccharomyces cerevisiae, a yeast species that is commonly used today. Most were beer strains but the team included a number of wine, spirit, sake and bread yeasts for comparison. They knew from past studies that it was common for organisms exposed to artificial selection to carry evidence of such tinkering in the form of duplicate chromosomes and genes. And, sure enough, they found these characteristics in abundance and noticed that all the strains seemed to stem from wild ancestors that lived 500 years ago.团队里的专家通过在怀特纯酵母发酵实验室(圣地亚哥的一家开发并销售酵母菌的公司)中研究， 研究人员分析了157种酿酒酵母(一类至今还被广泛地使用的酵母菌)的基因。用于实验的菌种大多数是啤酒菌种，不过还包括一定数量的葡萄酒、烈酒、日本清酒和面包菌种以便加以比较。他们从以往的实验中发现人人工培育通常会留下缝缝补补的痕迹——那些人工培育的微生物，常常都带有重复的染色体和基因。从这一点出发，他们果真发现了许多这类特征，并且还发现似乎所有的菌种都源自于500年前的野生菌种。

Expert：n. 专家;行家;能手Saccharomyces cerevisiae：酿酒酵母artificial selection：[遗] 人工选择;人为淘汰tinkering：n. 铸补，熔补duplicate：adj. 复制的;二重的chromosome：n. [遗][细胞][染料] 染色体stem from：起源于

Further support came from traits carried by their genes. All yeasts engage in asexual reproduction most of the time. But wild species are capable of mating when genetic diversity in a population declines. Such a trait can prevent populations from becominghomogenous and thus vulnerable to a single disease or predator, but it serves no purpose in populations living in stable, protected man-made environments and ought thus to fade away. This is precisely what the researchers found. More than 40% of the beer yeasts were found to be incapable of reproducing sexually, and the others showed dramatically reduced sexual fertility.它们的基因特性，进一步地支持了先前的猜测。大多数情况下，所有酵母菌都是无性繁殖的。不过野生菌种在菌种个体数量下降的情况下能够进行有性繁殖。这样的特质可以防止同质化，避免群体受到单一疾病或捕食者的侵害。不过该特性在群体生长的稳定时期并没有用，所以在人造环境的保护下这种特性应当会逐渐消失。这正是研究人员想要寻找的信息。研究发现超过40%的啤酒菌种不能够进行有性繁殖，其他菌种的有性繁殖能力也大大降低了。

asexual reproduction：无性繁殖homogenous：adj. [生物] 同质的;同类的predator：n. [动] 捕食者

Although domestication led sexual reproduction to decay, traits useful for life in abrewery became more common. The researchers found that genes involved in the fermentation of maltose, the main sugar found in beer, were duplicated several times, allowing beer yeasts to complete the fermentation process more rapidly than their feral ancestors. Similarly, wild yeasts typically carry genes associated with a range of unpleasant flavours; and these genes were rare in the culinary ones. Intriguingly, all these signs of domestication were far stronger in the 102 brewing strains that the researchers studied than those in the wine strains.尽管培育致使菌种的有性生殖能力衰减，但是对人类有益的特性却在啤酒厂里保存了下来。研究人员发现，在啤酒中的主要糖分，麦芽糖的发酵过程中，其基因被多次复制，促使发酵过程比其祖先——野生菌种要快得多。同样的，野生酵母通常都带有能发出让人不舒服味道的基因，并且这些基因在烹饪用的菌种中很罕见。有趣的是，在研究人员研究的这102种酿酒菌中，人工培育的啤酒菌种的这些特性都比葡萄酒菌种的要强的多。

Brewery：n. 啤酒厂Maltose：n. [有化] 麦芽糖Intriguingly：adv. 有趣地;有魅力地

The evidence suggests that yeast domestication began in the 1500s and was more pronounced in brewing than it was in winemaking. Drs Maere and Verstrepen suggest that this may be down to different practices. Brewing yeasts were likely to breed continuously in a man-made environment, since they are recycled after each fermentation batch and beer is produced all year. In contrast, wine yeasts are only grown for a short period every year, and spend much of their lives in and around vineyards where they are subject to intermingling with wild strains, so are subjected to natural selective pressures.(读者试译)证据表明酵母菌培育始于十六世纪，并且多用于啤酒酿造而非葡萄酒酿造。Drs Maere和Verstrepern认为，这可能是由于两者的酿造方法不同。啤酒可以全年酿造，并且每次发酵后还能回收利用，所以啤酒酵母可以人工环境下不停的繁殖。读者朋友们可以把自己的理解留言在文章下方，第二天会有解析哒。

Vineyard：n. 葡萄园Intermingle with：混合

The work was more than an academic exercise. The researchers went on to select a strain of beer yeast that shows very efficient fermentation, but also produces an unwantedspicy flavour, and crossed it with a less efficient but better-smelling sake strain. By selecting progeny without the gene variants for the off-flavour, they obtained a new beer yeast that combines swift fermentation with a lovely, fruity aroma. And this could be just the beginning. The scientists expect a range of novel yeast hybrids to follow from their research.本次研究不单单只是一次学术活动。研究人员随后还选出了一种啤酒酵母菌。这种酵母菌具备非凡的发酵能力，但也会产生一种讨厌的辛辣味。通过把它与一种发酵能力相对较低，但却好闻的清酒菌种杂交，再剔除那些带有能产生异味基因的杂交品种，研究人员得到了一种即带有芳香的水果气味，又能迅速发酵的新型啤酒菌。这或许仅仅只是一个开始。科学家们期望通过他们的研究，能生产出一系列新的杂交酵母菌。

Spicy：adj. 辛辣的Progeny：n. 子孙;后裔Aroma：n. 芳香