Bacteriophages -- phages for short -- are viruses whose hosts are bacteria. On Earth, bacteria are the most numerous organisms, viruses are even more abundant, and phages are the most prevalent of viruses. Phage numbers are estimated to be in the range of 10 to the 31st power worldwide; if each phage weighed a pound, their mass would equal the weight of the sun. There are a million or more phages per mililiter of sea water, roughly 10 billion per gallon. Of course, a phage doesn't weigh a pound, but taken together, their mass is equal to that of 100 million blue whales.

Phages may be the single most important contributors to bacterial evolution; They arguably are responsible for why aquatic photosynthetic bacteria are so diverse (Hutchinson's Paradox) and are main contributors to bacterial sex (transduction). The latter adds greatly to bacteria ecological versatility, evolutionary success, and clinical virulence. Phage evolution is fascinatingly complex in its own right, consisting of myriad combinations of disparate phage genomes (recombination) as well as a mixing together of phage with bacterial DNA.

At phage.org our aim is to provide a slice of phage ecology:

1. That concerning phage interaction with their environments (phage ecology)
2. Change in phage properties in the course of those interactions (phage evolution)
3. Phage uses as model organisims to better understand ecology and evolutionary biology more generally
4. And how as an illustration of applied ecology, phages may be used to both control and eliminate nuisance plus pathogenic bacteria (phage therapy)