SELECTION AND PROPERTIES OF TOTALLY PHAGE -RESISTANT MUTANT PSEUDOMONAS-PUTIDA PPG1

The efficiency of using bacteria in open systems to degrade different anthropogenic toxic pollutants dan depend strongly on the interaction between these bacteria and natural bacteriophages. The possibility of selecting bacterial Pseudomonas putida mutants resistant to all bacter iophages of this species known so far was tested (in our work, these m utants were designated totally phage-resistant mutants). In a model ex periment, changes in the composition of a population upon prolonged gr owth of bacteria in the presence of one of the virulent phages were ex amined. On the basis of the results obtained, it is postulated that: ( 1) Mutants differing in resistance to various phages accumulate in a p opulation; relative numbers of different mutants can undergo alteratio ns dyer the course of time; mutants selected in the presence of a give n virulent phage do not often manifest complete resistance to this pha ge. (2) It is possible to isolate totally phage-resistant mutants of P . putida PpG1. These mutants carry up to three different mutations sim ultaneously; however, these mutants regain sensitivity to many phages upon pseudoreversion occurrence.