If anything makes us human it’s our minds, thoughts and emotions.

　　如果有什么东西能够定义人类的话，那一定是我们的心灵，想法和情绪。

　　And yet a controversial new concept is emerging that claims gut bacteria are an invisible hand altering our brains.

　　然而，一个有争议的新概念正在出现，那就是，肠道细菌是一只看不见的手，它正改变着我们的大脑。

　　Science is piecing together how the trillions of microbes that live on and in all of us - our microbiome - affect our physical health.

　　科学正在试图了解，生活在我们所有人身上的数以万亿的微生物是如何影响我们的身体健康的。

　　But even conditions including depression, autism and neurodegenerative disease are now being linked to these tiny creatures.

　　但即使是抑郁症，自闭症和神经退行性疾病等疾病，现在也与这些微小的生物有关。

　　We’ve known for centuries that how we feel affects our gut - just think what happens before an exam or a job interview - but now it is being seen as a two-way street.

　　几个世纪以来，我们已经知道我们的感受如何影响我们的肠道，想一想在考试或面试之前会发生什么就知道了。但现在这被认为是互相影响的。

　　Groups of researchers believe they are on the cusp of a revolution that uses "mood microbes" or "psychobiotics" to improve mental health.

　　研究人员小组认为他们正处于一场使用“情绪微生物”或“精神活性物质”来改善心理健康的革命的风口浪尖。

　　The study that ignited the whole concept took place at Kyushu University in Japan.

　　点燃整个概念的研究发生在日本九州大学。

　　The researchers showed that "germ-free" mice - those that never came into contact with microbes - pumped out twice the amount of stress hormone when distressed than normal mice.

　　研究人员表明，“无菌”小鼠 - 那些从未接触过微生物的小鼠 - 在压力下比正常小鼠释放两倍量的应激激素。

　　The animals were identical except for their microbes. It was a strong hint that the difference was a result of their micro-organisms.

　　这些动物，除了其微生物之外，其余都是相同的。这强烈地暗示着，差异是由它们的微生物带来的。

　　There is now a rich vein of research linking germ-free mice with changes in behaviour and even the structure of the brain.

　　现在有大量的针对无菌小鼠与其行为变化甚至大脑结构之间的联系的研究。

　　But their completely sterile upbringing is nothing like the real world. We’re constantly coming into contact with microbes in our environment, none of us are germ-free.

　　但是，它们完全无菌的成长环境与现实世界并不相同。我们在环境中不断接触到微生物，没有人是无菌。

　　A good rule of thumb is a healthy microbiome is a diverse microbiome, containing a wide variety of different species living all over our bodies.

　　大致上，健康的微生物群是一个多样化的微生物群，包含各种不同的物种，遍布我们的身体。

　　And some lifestyles that weaken our gut bacteria, such as a diet low in fibre, can make us more vulnerable.

　　而一些削弱我们肠道细菌的生活方式，例如纤维含量低的饮食摄入，会使我们更加脆弱。