[Phage-stable mutants of Pseudomonas putida: new types of stability]

More than 170 phage-resistant mutants (PRM) of the first order of Pseudomonas putida strain PpG1 were obtained using newly isolated and previously described bacteriophages specific for this strain. According to the results of analysis of resistance of the mutants to each of 31 phages of PpG1 strain and 8 phages of the PpN strain, the PRM strains were distributed into 20 groups. In most cases, the reason for resistance is loss of absorption capacity of bacteria. However, no direct relation between the level of absorption and efficiency of phage plating was detected. It was shown that some of the PRM of P. putida PpG1 strains acquired the ability to maintain the growth of phages specific for the other P. putida strain, PpN. Frequencies of isolating mutants of various resistance types depend on the concrete phage used. In accordance with their absorption specificity, all phages were distributed into 23 groups, and a tridimensional formal scheme of receptor sites for these phages on the PpG1 strain was drawn. In the process of selection of the PpG1 clones resistant to non-lysogenizing mutant of temperate PP71 phage, a variant of this strain manifesting the phenomenon of "auto-plaquing" was found. These results support the mutational origin of this phenomenon in some cases.