Viruses most likely make up a very large part of the mass of the biosphere. Most scientists would argue that viruses are not living organisms but rather a very efficient molecular form of parasites. Consider for a moment that each organism appears to be able to be infected by a large number of viruses and many of them are unique for the organism and hence there are more types of viruses out there than there are living agents.

Viruses are very small, too small to be seen with the light microscope. However although they are small they are mighty. One of the properties of many types of viruses once they take over a cell is to eventually destroy the host cell. Prior to killing the host most viruses produce many copies of itself, ready and waiting and poised to attack the surrounding cells. If this cycle proceeds on a Petri dish one can note a zone of death of the host bacteria referred to as a plaque. A virus that infects bacteria is known as a bacteriophage because of the zones of death that they form on a plate makes it appear as if the bacteria had been eaten.

The following pages will describe how to isolate bacteriophage from environmental samples. We will provide you with plates containing media, protocols, and any additional assistance you will need to isolate bacteriophage. Of particular note are the bacteriophage isolated that infect Mycobacteria. There is great interest in these viruses as they may be useful as a way to stop one organism of that genus - Mycobacterium tuberculosis, the causative agent of tuberculosis. It may also be possible for you to study your virus further through a mini-grant process by a lab interested in studying these viruses.