Bacterial cells are small, one to two microns in diameter and this shows a picture of a common bacterium called E. Coli.

细菌细胞很小,直径只有一到两个微米,这张图片是一种常见细菌,大肠杆菌

耶鲁公开课 - 生物医学工程探索课程节选

It's a common bacterium and most strains of E. Coli are not harmful to people, in fact, they provide us with some beneficial properties.

它是常见菌,且大多数种类的菌株对人类无害,实际上还给了我们颇多裨益

耶鲁公开课 - 生物医学工程探索课程节选