Adsorption of bacteriophages specific for Pseudomonas aeruginosa R factors RP1 and R1822

Short, thick pili were found by electron microscopy on bacteria carrying the P group drug resistance plasmids RP1 and R1822. The R1822-specific phage PRR1 was seen to adsorb to the bases of the pili. Three RP1-specific phages, one filamentous (Pf3), and two with very thick capsids (PR3, PR4), were seen to attach all around the surface of $\text{P. aeruginosa}$ cells, and were thought to be somatic, since pilus phages appear to be strictly polar on this species. PR3 and PR4 also lysed a strain of $\text{E. coli}$ containing an N group plasmid, suggesting a relationship between the N and P group plasmids.