title: Characterization of phage 18, an unstable coliphage.
abstract: Phage 18, a noninducible coliphage, is quite unstable and therefore difficult to study. Newly developed very gentle lysis and mounting techniques yielded isolated virions for examination by electron microscopy. The phage has a contractile tail with a length of 130 nm and an isometric head with a capsid diameter of 50 nm. Phage 18 is similar in morphology to phage P2 but is heteroimmune to it. DNA extracted from a clear-plaque mutant of phage 18 was subjected to BamHI restriction endonuclease digestion and was found to be easily distinguishable from the published restriction patterns for P2, phage 299, or phage 186 DNA. The genome size was calculated to be 33.5 kb. Using the DNA melting point, phage 18 DNA (G+C) content was determined to be 55.0% and its buoyant density was determined to be 1.715.
mesh_terms: D003090:Coliphages / Q000145:classification* / Q000254:growth & development / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000032:analysis; D004279:DNA, Viral / Q000032:analysis; D004926:Escherichia coli / Q000145:classification* / Q000254:growth & development / Q000648:ultrastructure; D008854:Microscopy, Electron; D009154:Mutation; D009691:Nucleic Acid Denaturation
chemical_list: D004269:DNA, Bacterial; D004279:DNA, Viral