I was surprised to find this in wikipedia [1]: A strain of bacteria, or any microorganism that causes illness or has a superficial resemblance to an insect

I was surprised to find this in wikipedia [1]: A strain of bacteria, or any microorganism that causes illness or has a superficial resemblance to an insect or bug I think it's quite confusing to call bacteria, bug. But I'm not a native speaker. Is this common usage? 1: http://en.wikipedia.org/wiki/Bug http://en.wikipedia.org/wiki/Bug