AIM:Determine the possibility of Iysogenization of Escherichia coli single strain DNA (ssDNA) by 1ø7 bacteriophage from the Microviridae family and determine the role of phage lø7 lysogeny in genetic variability of these bacteria.MATERIALS AND METHODS:A method of E. coli K12 lysogenization by phage lø7 was developed. A spot-test for the control of resistance of the obtained lysogens against phage lø7 and determination of lysogen lø7 spontaneous production was worked out. Criteria for phage lø7 identification, that is spontaneously produced by E. coli K12 lysogens, were proposed. A kit of isogenic E. coli strains, that vary by mutations in ptsI, ptsH and fruA genes, that code phosphoenolpyruvate (PEP): carbohydrate phosphotransferase system (PTS) proteins, was constructed.RESULTS:The ability of highly virulent bacteriophage lø7 to lysogenize E. coli was shown. A reduction of lø7 titers in ptsI, ptsH and fruA E. coli K12 mutants was demonstrated compared with titers in wild-type bacteria. Lytic bacteriophage lø7 was also able to lysogenize ptsI, ptsH and fruA mutants at a high frequency. Lysogens are resistant to phages lø7, phiX174 of Microvirus genus and spontaneously produce lø7.CONCLUSION:Bacteriophage lø7 of the Microviridae family is able to lysogenize E. coli K12 and vertically transfer genome of this lytic phage. As a result, lytic phage lø7 takes part in bacterial variability as a factor of lysogen selection in bacteria population corresponding to PTS mutants by phenotype.

A computer-aided analysis of the repeating sequence of Bordetella pertussis chromosome (RSBP3) revealed 3 open reading frames, one of whose (ORF1) can code a protein whose structure and properties are similar to those of transposasas, i.e. enzymes in charges for the traveling of migrating genetic elements of pro- and eukaryote. Mutants of the RSBP3 insertion sequence with the affected and unaffected ORF1 sequence were constructed in order to substantiate the above assumption. Two independent experimental models (formation of inter-plasmid co-integrates and of co-integrates between plasmid and E. coli chromosome) were used to show that the RSBP3-stimulated formation of co-integrates is only true for plasmids containing RSBP3 with the unaffected ORF1 sequence. An activity of the Hpr protein (a component of the phosphoenolpyruvate-dependent phosphotransferase) was proven to influence the formation process of inter-plasmid co-integrates.

Mutational damage of the ptsH gene leads to pleiotropic disturbance of sugar utilization in Escherichia coli K12. A fruS mutation suppresses the defect because of a constitutional expression of the fruB and fruA genes. FruB protein possessing a pseudo-HPr activity replaces the HPr. It was shown that wild type allele fruS+ dominates over the fruS1156 mutation in heterozygous merodiploid. The existence of thermosensitive mutations (fruS4 and fruS12) which repair the ptsH damage was also demonstrated. The fruS mutations were located in the fru operon. Fructose utilization was not disturbed in fruS1156 mutant, but fruS2 and fruS12 mutants were unable to utilize fructose. Spontaneous mutations (fruS6 and fruS13) possessing the same phenotype at any temperature similar to the thermosensitive ones under nonpermissive conditions were isolated. They were mapped using the P1vir transduction. The fruS mutations were found in the structural gene of the fructose operon. Presumably it is the fruA gene that cods for the fructose-specific multidomain protein IIB'Bc of the phosphoenolpyruvate-dependent phosphotransferase system.

The present work analyzes pt44 mutation in Sh. flexneri resulting in the appearance of the following phenotypical properties: resistance to phosphomycin, avirulence, pleiotropic disturbances in carbohydrate utilization. The data provided by the biochemical and genetic analysis have indicated that pts44 mutation occupies the region between purC and ptsI loci on the chromosome of Sh. flexneri. Merodiploids containing the mutant allele pts44 and the plasmid including purC-ptsI-ptsH genes from E. coli K12 acquired the capacity for fermenting carbohydrates, but at the same time retained resistance to phosphomycin and avirulent properties. The presence of phosphoenol pyruvate-dependent carbohydrate phosphotransferase system in Sh. flexneri has been proved.

The object of this work was to study the effect of mutations damaging protein components of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) of E. coli on the regulation of the activity of catabolite-sensitive operons. Mutations ptsI and ptsH affecting the activity of the enzyme I and HPr protein made the synthesis of catabolite-sensitive enzymes resistant to the action of glucose, and at the same time decreased the rate of transport of this compound. Mutation tgl affecting the activity of the glucose enzyme II lead to the same effect on the enzyme syntheses, though utilization was not altered in this case. The disturbance of beta-galactosidase synthesis in ptsI and ptsH mutants is due to interference of pts mutations into transcription of the lac operon at the lac promoter level. It is concluded that the proteins of the Escherichia coli PTS take part not only in glucose transport, but are also involved in the regulation of transcription of the catabolite sensitive operons.