SOME FEATURES OF ESCHERICHIA-COLI MU-PHAG E GROWTH IN PSEUDOMONAS-AERUGINOSA

In order to determine the replication-transposition (RT) efficiency of Escherichia coli phage Mu in Pseudomonas aeruginosa cells, the change of Mu DNA copy number after transfer of P. aeruginosa (RP4=Mu) from 4 2 (the condition of RP4=Mu plasmid stability and low phage production level in P. aeruginosa) to 30-degrees-C (the condition of RP4=Mu plasm id instability and higher phage production level in P. aeruginosa) was analysed. It was shown that the temperature shift causes no increase in Mu DNA copy number, although free phage DNA is revealed after trans fer of the cells at 30-degrees-C. Considering that the studied cells c ontained also a linear RP4 DNA and the free Mu DNA hybridized with the RP4 DNA, we proposed that the mature Mu DNA arises as a result of Mu genome packaging from the original plasmid. So, the Mu genome RT is un effective in P. aeruginosa and all of the phage particles released fro m P. aeruginosa (RP4=Mu) cells contain Mu DNA apparently originated fr om the DNA of hybrid plasmid RP4=Mu. Moreover, these results suggest t hat the Mu DNA packaging is not effective in P. aeruginosa (taking int o account that the P. aeruginosa (RP4=Mu) cells release about 10(-2) p .f.u./cell and that originally the copy number of RP4=Mu greater-than- or-equal-to 1).