Phage X: A Plasmid-dependent, Broad Host Range, Filamentous Bacterial Virus

Abstract

Phage X was isolated from sewage by plating on Escherichia coli or Salmonella typhimurium strains harboring the incompatibility group X plasmid R6K. It also plated on a strain of Serratia marcescens carrying this plasmid. It failed to form plaques on Proteus mirabilis, P. morganii or Providencia alcalifaciens harboring R6K, but did multiply on them. No phage increase occurred with homologous R- strains. Phage X also plated or registered an increase in titer on E. coli or S. typhimurium strains carrying various plasmids of incompatibility groups M, N, P-1, U or W and the unassigned plasmid R775. It adsorbed to pili determined by a group of P-10 plasmid in a Pseudomonas aeruginosa strain but did not multiply on this organism. The phage was filamentous and curly, resistant to RNase and diethyl ether and sensitive to chloroform. It adsorbed to the tips of pili.