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。
The rest are all hitch-hikers, mainly harmless bacteria that have evolved with us.
伯明翰大学的科学家发现，以糖为生的无害细菌能产生氢气。
Scientists at the University of Birmingham have shown that harmless bacteria that feeds on sugar produces hydrogen gas.
他们发现在典礼前，即使在涂抹了大量消毒剂后，手上仍然存在大量的无害细菌。
They found that before the ceremony, and even after a slathering of sanitizer, hands were home to plenty of nonharmful bacteria.
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