phage

phage (fāj) bacteriophage.

---

phage (fj)

n.

See bacteriophage.

---

phage.

See bacteriophage.

---

bacteriophage [bak-te´re-o-fāj″]

a virus that destroys bacteria by lysis; several varieties exist, and usually each attacks only one kind of bacteria. Certain types attach themselves to the cell membrane of the bacterium and instill a charge of DNA into the cytoplasm. DNA carries the genetic code of the virus, so that rapid multiplication of the virus takes place inside the bacterium. The growing viruses act as parasites, using the metabolism of the bacterial cell for growth and development. Eventually the bacterial cell bursts, releasing many more viruses capable of destroying similar bacteria. Called also bacterial virus. adj., adj bacteriopha´gic.

With some bacteria, notably those of the Streptococcus family, infection by certain phages can dramatically alter pathogenicity, converging previously innocuous microbes into deadly pathogenic strains. The so-called “flesh-eating” viruses are a striking example. They are relatively harmless bacteria until new geletic material is incorporated via a phage or plasmid.

temperate bacteriophage one whose genetic material (prophage) becomes an intimate part of the bacterial genome, persisting and being reproduced through many cell division cycles; the affected bacterial cell is known as a lysogenic bacterium.

---

phage

see bacteriophage.

---

phage type

an intraspecies type of bacterium demonstrated by phage typing; called also lysotype and phagotype.

phage typing

characterization of bacteria, extending to strain differences, by demonstration of susceptibility to one or more (a spectrum) races of bacteriophage; widely applied to staphylococci, typhoid bacilli, etc., for epidemiological purposes.