Partial genetic characterization of FIZ15 bacteriophage of Pseudomonas aeruginosa

FIZ15 phage of Pseudomonas aeruginosa causes lysogenic conversion in PAO1 strain. Lysogen shows increased adhesion to human buccal epithelial cells, increased resistance to 75 percent human serum bactericidal effect, and streptomycin resistant. These phenotypes apparently are due to a phage-induced superficial change on its own bacterial receptor, which probably is the O-antigen. In order to begin FIZ15 characterization, nitrous acid-induced clear-plaque mutants were obtained. They belonged to three complementation groups and mapping by two factor crosses revealed that they were closely linked. In a search for phage mutants that do not cause lysogenic conversion, two streptomycin-sensitive mutants were obtained by ethyl methane sulphonate mutagenesis of PAO1 lysogenic for FIZ15 (PIZ15 strain). One mutant (con1) showed and adhesion value similar to that of PAO1 and the other (con2) had an adhesion twofold and 1.3 times greater than PAO1 and PIZ15, respectively. con1 did not show increased serum resistance, whereas con2 was as resistant as PIZ15. Phages were isolated from the streptomycin sensitive mutants and used to relisogenize PAO1 to obtain the con1d and con2d lysogens. Adhesion and serum sensitivity of con1d was identical to that of PAO1 but con2d behaves like PIZ15. FIZ15 phage was unable to adsorb to PIZ15, con2 and con2d. On the other hand, FIZ15 phage adsorbs well to con1 and con1d but not to PIZ15. These results suggest that con1 mutation lies on the phage chromosome and con2 on the bacterial one. Finally, adhesion of all lysogens and PAO1 was stimulated 2-3 times by KCl and this effect was suppressed by and oxidative phosphorylation uncoupler.