An estimated 1030–1032 phages exist in the biosphere, and an estimated 1023 phage infections occur per second. Every 48 hours, phages destroy about half the bacteria in the world, a dynamic process that occurs in all ecosystems.
Potera, Carol, "Phage Renaissance: New Hope Against Antibiotic Resistance." Environmental Health Perspectives, 1 Feb. 2013. Web.
As a January 2, 2015 article for the Internet news site Buzzfeed aptly described, "[p]hages are bacteria's natural enemies . . . [t]hey are the most common and diverse organisms on Earth, and each phage harms only specific strains of bacteria. When you turn on the faucet, millions of phages flow out with your tap water. That leaves a nearly inexhuastible supply of potential agents to use in the fight against infection."1 Phages "can be found virtually everywhere - in soil, drinking water, sewage. In fact, each one of us naturally has billions of them in our bodies.2
According to a 2013 Environmental Health Perspectives report, phages are "natural viral predators which target bacteria but leave mammalian and plant cells unscathed."3 Indeed, as possibly "the oldest . . . organisms on Earth . . .[,] phages play a key role in maintaining balances in every ecosystem where bacteria exist."4
Phages destroy bacteria through a natural process called lysis, which begins when phages latch onto specific receptors located on the outside of the bacterial cell wall. The phages inject their own DNA into the bacterial body, and then proceed to replicate; effectively "hijack[ing] the cell's reproductive machinery" to produce hundreds of new phages.5 The replication process continues until the bacterial cell wall explodes, killing that bacterial cell and ejecting the new phages into the surrounding environment in search of other bacteria to attack. Once the particular bacterial strain which nature designed specific phages to attack are no longer present; then, "[i]n the absence of target bacterial species, phages are quickly eliminated from the body."6