The rest are all hitch-hikers, mainly harmless bacteria that have evolved with us.

其它的都是搭便车的生物，主要是一些与我们共生的无害细菌。

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Researchers at the Cork Cancer Research Centre (CCRC) have found that harmless bacteria from probiotic yogurt (bifidobacteria) naturally travels through the body and can grow inside tumors.

科克癌症研究中心(CCRC)的研究人员发现，酸奶中的益生菌(双歧杆菌)可以天然地通过人体并且在肿瘤中生长。

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So Barbeito and three volunteers grew their own beards for 73 days, then sprayed them with harmless bacteria and demonstrated that it was harder to wash the germs out of a beard than off clean skin.

所以Barbeito和三位志愿者做了如下实验：他们连续73天不刮胡子，然后在胡子上喷洒一种无害的细菌，并证实在这种情况下，细菌比没有胡子的时候更难以清洗。

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They may even use harmless bacteria as a transport link to arm other harmful bugs that pass by.

FORBES: Germ Warfare

The harmless bacteria - belonging to the Bacillus genus - then feed on the nutrients to produce limestone.

BBC: Key test for re-healable concrete

There is no need to panic, however: the creatures in question are harmless bacteria that were found preserved in a crystal of rock salt.

ECONOMIST: Old salts