Suppressor Mutation in Pseudomonas Aeruginosa

Suppressor mutations were identified in Pseudomonas aeruginosa, and a comparison was made with Escherichia coli suppressor systems. A suppressor-sensitive (sus) derivative of a plasmid, RP4 trp, and several Sus mutants of IncP1 plasmid-specific phages, were isolated by using E. coli. Plasmid RP4 trp (sus) was transferred to P. aeruginosa strains carrying trp markers which did not complement RP4 trp(sus), and Trp+ variants were selected. Some, but not all such revertants, could propagate PRD1 Sus phages, and these mutants were found to be supressor positive. Plating efficiencies of various Sus phages on these strains were compared with on E. coli strains carrying known suppressor genes. The results suggested that the Pseudomonas suppressors were probably amber suppressors. In iddition, some Sus phages (PRD1sus-55, PRD1sus-56) were obtained which, although apparently of the amber type for E. coli, were able to propagate equally well on sup+ or sup strains of P. aeruginosa. On the other hand, several mutants of phage PRR1 which were suppressed in E. coli were not suppressed by the P. aeruginosa suppressor. Suppressor-sensitive mutants were also isolated with P. aeruginosa bacteriophages E79 and D3.