title: Phages I alpha and I2-2: IncI plasmid-dependent bacteriophages.
abstract: Phage I alpha was isolated from sewage from Windhoek, South West Africa. It formed relatively clear plaques about 2 mm in diameter, on sensitive strains of Escherichia coli K12 and Salmonella typhimurium LT2. The phage had an hexagonal outline with a diameter of about 24 nm, contained RNA and was resistant to chloroform. Phage I alpha formed plaques or propagated only on organisms carrying I1 plasmids or the I gamma plasmid R621a. The efficiency of plating was higher on E. coli than on S. typhimurium hosts. The phage adsorbed along the length of shafts of I1 pili. Phage I2-2 was isolated from Pretoria sewage. It was a filamentous virus and individual virions varied considerably in length. Phage I2-2 formed turbid plaques which varied from pin point to about 1 mm in diameter on all hosts. It was resistant to RNAase and sensitive to chloroform. Phage I2-2 had a spectrum of activity limited to strains harbouring I2 plasmids but the adsorption site could not be demonstrated. The phage was not related serologically to phages Ifl or PR64FS.
mesh_terms: D001434:Bacteriophage Typing; D001435:Bacteriophages / Q000235:genetics*; D003090:Coliphages / Q000235:genetics / Q000648:ultrastructure; D004926:Escherichia coli / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000648:ultrastructure; D008854:Microscopy, Electron; D010957:Plasmids; D012483:Salmonella Phages / Q000235:genetics; D012486:Salmonella typhimurium / Q000235:genetics; D014771:Virion / Q000648:ultrastructure; D014776:Virus Cultivation