你還在喝酸奶養生嗎？新研究告訴你，益生菌喝錯了有害無利！
益生菌作為一種「好」細菌被賣給我們，它能幫助我們平衡腸道中各種「壞」微生物。但在老鼠身上的一項新實驗表明，我們的微生物盟友是如何進化成可能對我們的腸道造成損害的背叛者的。
Probiotics are sold to us as "good" bacteria that help balance out "bad" varieties of microbes camping out in our gut. But a new experiment on mice has shown how our microbial allies can evolve into traitorous backstabbers that risk causing damage to our guts.
病理學家兼生物醫學工程師Gautam Dantas說:「如果我們要把生物作為藥物來使用，我們需要認識到它們會適應環境，這意味著在體內呆了幾個小時的東西不一定和你放入身體的東西是一個。」
"If we"re going to use living things as medicines, we need to recognise that they"re going to adapt, and that means that what you put in your body is not necessarily what"s going to be there even a couple hours later," says pathologist and biomedical engineer Gautam Dantas.
「沒有一種微生物對進化免疫。」
"There is no microbe out there that is immune to evolution."
丹塔斯和他所帶領的來自華盛頓大學的研究團隊，評測了一種被營銷能用於對抗腹瀉的細菌:EcN。
Dantas led a team of researchers from the University of Washington who evaluated a bacterium marketed to help combat diarrhoea: EcN.
為了評估EcN被吞食後的進化潛力，研究小組使用了完全無菌的特殊培育小鼠。
To evaluate the potential of EcN"s evolution after it"s swallowed, the research team used mice specially bred to be completely germ free.
實驗對象被分成四組，每組都有一個獨特的腸道微生物群。一個完全無菌;另外三組給予反映各種健康和不健康狀態的微生物群落。
The test subjects were divided into four groups, each with a distinct gut microbiome. One was left completely sterile; the other three were given microbiomes reflecting various healthy and unhealthy states.
每一組都被給予EcN，然後餵食以下選項之一——乏味的一般實驗鼠糧，更自然的老鼠友好型飲食，高脂肪和高糖的西式飲食，以及添加了一些纖維的西式飲食。
Each group was dosed with EcN and then fed one of the following options - boring old lab mouse chow, a more natural mouse-friendly diet, a Westernised diet high in fats and sugars, and a Westernised diet that had some fibre added.
五周後，檢查了老鼠的腸道。還是那些快樂的小大腸桿菌？事實證明，它們並不都像剛來的時候那麼友好，尤其是那些處於不得不應對不健康的飲食的腸道里的。
Five weeks later, the mice had their guts examined. Those happy little E. coli? It turns out they weren"t all quite as friendly as they had been on their way in, especially in guts that had to deal with less than healthy diets.
在裝滿西式食物的老鼠腸胃中，EcN累積突變以應對壓力，和利用所有這些碳水化合物來比預期的逗留時間呆更久。
Inside mouse guts filled with westernised foods, EcN had accumulated mutations that helped them cope with stress and make use of all of those carbohydrates to hang around longer than intended.
