[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 can depend strongly on the interaction between these bacteria and natural bacteriophages. The possibility of selecting bacterial Pseudomonas putida mutants resistant to all bacteriophages of this species known so far was tested (in our work, these mutants were designated totally phage-resistant mutants). In a model experiment, changes in the composition of a population upon prolonged growth of bacteria in the presence of one of the virulent phages were examined. On the basis of the results obtained, it is postulated that: (1) Mutants differing in resistance to various phages accumulate in a population; relative numbers of different mutants can undergo alterations over the course of time; mutants selected in the presence of a given virulent phage do not often manifest complete resistance to this phage. (2) It is possible to isolate totally phage-resistant mutants of P. putida PpG1. These mutants carry up to three different mutations simultaneously; however, these mutants regain sensitivity to many phages upon pseudoreversion occurrence.