bacterium

Instead, the offending bacterium, known as Clostridium tetani, infects the body through cuts and abrasions.

Even worse, for a bacterium or virus your body is a hostile ecosystem applying selective pressure.

It has a gene from corn and a gene from a bacterium that allow it to produce tons of beta-carotene, which in turn produces Vitamin A.

It's caused by a parasite, not a virus or bacterium.