[Duplication in the region of the phoA and lacZ genes on the Escherichia coli K-12 chromosome]. / Izuchenie duplikatsii v raione genov phoA i lacZ na khromosome Escherichia coli K-12.

Transduction of genetic markers phoA1::Tn5 and lacZ::Tn10 was used to show the high frequency of occurrence of duplication (5-8%) carrying the above mentioned genes without application of selection for the increase of their function. Genetic tests were used to show that duplicated segments vary in size and in some cases comprise the whole lacZ-phoA region of Escherichia coli K-12 chromosome.

[Methyl-cytosine specific restriction in Escherichia coli K-12]. / Izuchenie metil-tsitozin spetsificheskoi restriktsii u Escherichia coli K-12.

Experiments on transformation of Escherichia coli K-12 cells by plasmids carrying RM systems with different recognition sites containing 5-methylcytosine have shown that the gene mcrB determines the function of restriction. The data obtained made it possible to believe that E. coli possesses no restriction system recognizing specifically cytosine methylated in position 4.

[Precise mapping of the gpp gene involved in guanosine tetraphosphate synthesis and ilvC-gpp deletion in the region of the Escherichia coli chromosome]. / Tochnoe kartirovanie gena gpp, uchastvuiushchego v sinteze guanozintetrafosfata, i poluchenie deletsii ilvC-gpp v oblasti khromosomy Escherichia coli.

Using the set of transducing lambda phages the gpp gene, responsible for pppGpp to ppGpp conversion, was localized between rep and trxA genes on 85 min of the Escherichia coli genetic map. Taking advantage of the Tn10 transposon inserted into the adjacent ilvY locus, we deleted the region of E. coli chromosome covering ilvC, rep and gpp genes. The metabolism of (p)ppGpp in the deletion-containing cells confirms that the product of the gpp gene, guanosine pentaphosphatase, is not the only enzyme, responsible for pppGpp degradation and ppGpp synthesis.

[Inversion of the metE-oriC-rpsE chromosome segment in Escherichia coli K12]. / Inversiia segmenta khromosomy metE-oriC-rpsE u Escherichia coli K-12.

We have described recently a large inversion of the Escherichia coli chromosome (designated udpPf1), including region of the chromosomal replication region (oriC). The udpPf1 inversion was induced by Tn10 transposon (metE::Tn10). It results in increased expression of the uridine phosphorylase gene (udp) which is closely linked to the metE gene. The data of conjugational and transductional experiments presented in this report demonstrate that the udpPf1 inversion covers a chromosomal segment extending over 12 min of the E. coli genetic map and including the rpsE, crp and metE::Tn5 markers. The results are presented indicating that the increased uridine phosphorylase activity is due to fusion of the udp gene to a more strong promoter located, probably, in the operon for ribosomal proteins cluster, near 73 min on the E. coli chromosome.

[Large deletions in the region of the replication termination of Escherichia coli K-12 chromosome]. / Protiazhennye deletsii v oblasti terminatsii replikatsii khromosomy Escherichia coli K-12.

The Escherichia coli strain PLK1427 (Henson, Kopp, Kuempel, 1984) was used in this work. It carries a deletion of 60 thousand pairs of nucleotides in the chromosomal region 30-31 min and a partially deleted prophage lambda rev cI875Sam7 integrated into the 30 min region, instead of the rac prophage. Among the mutants of PLK1427 strain selected for resistance to 42 degrees C, deletions extending about 4 min and affecting the loci nirR (29.3 min), zdc235::Tn10 (32.3 min) and zdd230::Tn9 (33.3 min) were found. Although the deletion mutants obtained affect the region of replication termination (terC) of the chromosome, they have no alterations in the growth rate. It was demonstrated that some deletions may be transferred and are capable of recombination, giving the wild type in transductional experiments with the mutant phage T4.

[Generation of deletions in the region of the crp gene on the Escherichia coli chromosome]. / Poluchenie deletsii v oblasti gena crp na khromosome Escherichia coli.

Deletions in the argD, crp, cysG genes (73-74 min of the Escherichia coli genetic map) were obtained by heat induction of the phage lambda c1857 b221 rex::Tn5 integrated previously into the cysG gene by homologous recombination in the cysG::Tn5 mutant. Properties of the deletions obtained suggest the gene order: argD-crp-cysG.

[Chromosomal inversion accompanied by an enhancement of uridine phosphorylase gene expression in Escherichia coli K-12]. / Inversiia khromosomy, soprovozhdaiushchaiasia usileniem ékspressii gena uridinfosforilazy u Escherichia coli K-12.

In thymine requiring auxotrophs of Escherichia coli the uridine phosphorylase enzyme (udp gene) can catalyze nonspecifically conversion of thymine to thymidine. By selection for effective utilization of exogenous thymine, it is possible to isolate forms with increased expression of the udp gene. Mutants with increased gene expression were isolated from the strain with transposon Tn10 within the metE gene closely linked to udp. Some mutants (designated udpPf) losing Tn10 but retaining the Met- phenotype are characterized by disturbance of recombination in the metE-udp region: they do not form Met+ transductants in P1 transduction with the wild-type donor strain. However, recovery of homology in the chromosomal metE-udp region takes place with low frequency in P1 transduction using the strain with Tn10 insertion in metE as a donor. Data obtained in transductional and conjugational experiments demonstrate that the udpPf1 mutant studied is an inversion extending about 3 min of the E. coli chromosome and including the region of chromosomal replication origin (oriC).