system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Bacteriophage. Why are they different than normal bacterium, why are they shaped that way?
gpt
A bacteriophage is a virus, not a bacterium. It gets its name because instead of infecting large animals (humans) like most viruses you are familiar with, it attacks bacteria. The name literally means bacteria-eater.

It latches onto the outside of the bacterium with it's tripod of claws and stings the bacterium with its stinger, thereby infecting it. The sting forces the bacterium to start growing new viruses inside it. Eventually the bacterium gets to be so full of baby viruses it explodes, releasing the viruses and dying in the process. Then the new baby viruses are free to find new bacteria to make their victims.

This process is not necessarily a good thing. There are good bacteria that we don't want killed, and there are some bacteria which have poison on the inside which is released when they are killed by the virus (doing more damage to the person they're inside, than the bacterium would have if left alone). In some cases however, the bacteriophages can be a very useful in killing a stubborn infection (drug resistant flesh-eating bacteria for example).