It's really a drag to get sick. Wouldn't it be nice to know that germs can get sick, too? Well, you're in luck! It may cheer you up to know that bacteria can be infected by a type of virus known as a bacteriophage, which means "bacteria eater."
Bacteriophages are much smaller than bacteria, and--like all viruses--are incapable of growing and multiplying on their own. So they need to find a host in order to replicate themselves. That's why they attack bacteria.
Usually, the targets are super-specific, which means that a particular phage can only attack one type of bacterium, which it does by attaching to the cell wall and inserting its own genetic material into the cell body. The bacteriophage's genetic material takes over the bacterium's cellular machinery and reprograms it to produce more bacteriophages. Eventually, the host produces so many of them it literally bursts, enabling the new bacteriophages to spread to other bacteria.
Ever since bacteriophages were discovered, scientists have been experimenting with using them to fight diseases like cholera and, more recently, anthrax.