This is Scientific American — 60-Second Science. I'm Christopher Intagliata.
Immigrants to the U.S. might lose touch with certain customs and traditions back home. But here's something else they lose: their microbes. "When they came to the U.S. almost immediately they began losing their native microbes." Dan Knights, a computational biologist at the University of Minnesota. "And over time the balance shifted to the point where they were dominated by the U.S. associated microbes."
He's referring to first- and second-generation immigrant women, from the Hmong and Karen ethnic minorities in southeast Asia. His team sequenced the DNA found in their feces. And they saw that there was an immediate decline in the number and diversity of gut microbes among the immigrants, compared to their counterparts still living back home. And the decline continued over time.
If you're thinking, well, maybe the women just switched up their diets — started eating more hamburgers, more bacon and eggs? Dietary surveys don't bear that out. The women weren't changing their diets nearly fast enough to explain the drop in diversity. "So it seems as though there's something else going on that has to do with the U.S. lifestyle... Antibiotics could be playing a role. The water supply could be playing a role. It could be other aspects of lifestyle, stress, exercise, hygiene. But we don't have enough information yet to be able to pin it down." The results are in the journal Cell.
Some of the missing microbes helped digest traditional foods like tamarind, palm and coconut. But the consequences could be more severe than indigestion. "We have evidence from many studies now, especially even causal evidence in a number of animal studies, that having the wrong set of microbes, or missing the right set of microbes, can cause many of the diseases that are rising in industrialized nations." Things like obesity, metabolic disease. Which we might be able to fix, he says, if we're able to solve this microbial mystery.
Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.
移民美国者可能会与丢失家乡的某些习俗和传统 。但同时失去的还有一样东西：他们体内的微生物 。“移民来到美国后，他们体内的原有微生物就会马上开始流失 。”明尼苏达州大学的计算生物学家丹·奈特说到 。“随着时间的推移，他们体内的平衡状态会转变为由美国相关微生物主导 。”
他指的是来自东南亚苗族和克伦族等少数民族的第一和第二代女性移民 。他的团队对这些移民粪便中的DNA进行了测序 。他们发现，与生活在故乡时相比，这些移民在进入美国后，其肠道微生物的数量和多样性立即下降 。而且随着时间的推移，这种下降趋势会一直持续下去 。
如果你认为，也许这些女性只是改变了她们的饮食——开始食用更多的汉堡、培根和鸡蛋 。可饮食调查结果并不支持这种想法 。这些女性改变饮食的速度，不足以解释肠道菌群多样性下降的原因 。“这似乎与与美国生活方式的其它因素有关 。抗生素可能发挥了作用 。水源供应也有影响 。又或者与生活方式的其它方面、压力、锻炼和卫生也有关 。但我们目前还未掌握足够的信息，所以无法确定 。”研究结果发表在《细胞》期刊上 。
一些消失的微生物可帮助消化酸角、棕榈和椰子等传统食物 。但微生物消失的后果可能比消化不良更加严重 。“我们从许多研究中获得了证据，尤其是多个动物研究提供了因果性证据，能证明错误的微生物组合或者说微生物构成不当可能导致许多疾病，而且这些疾病在工业化国家的发病率正在不断增加 。”比如肥胖症和代谢性疾病等 。他说，如果我们能解开这个微生物谜题，那我们或许就能解决这些疾病 。
谢谢大家收听科学美国人——60秒科学 。我是克里斯托弗·因塔利亚塔 。
1. lose touch with (与…)失去联络；(与…)失去联系；
I've lost touch with all my old friends.
2. bear out 支持，证实（某人的说法）；
The other witnesses will be ar out what I say.
3. as though 好像；仿佛；
I thought it looked as though the battery was going.
4. pin down 确定；证实；
It has taken until now to pin down its exact location.