Biomedical subjects

V N Krylov

Publications and source records attributed to V N Krylov.

At least 55 records · Page 3Linked to original sources

PubMed1993

[The effect of certain Escherichia coli genes on the appearance of the TCS phenotype, conferred by plasmid RP4 with an integrated genome of the D3112 Pseudomonas aeruginosa phage].

The possibility of the SOS system activation caused by introduction of a hybrid plasmid RP4::D3112 (where D3112 is a genome of the transposable phage of Pseudomonas aeruginosa) into Escherichia coli was examined. It has been shown previously that the presence of this plasmid confers to E. coli a so called TCS phenotype: E. coli (RP4::D3112) forms normal colonies and grows at 42 degrees C but does not divide and becomes filamentous at 30 degrees C, probably because of E. coli DNA damages generated in the course of D3112 replication-transposition. It was shown that the level of prophage lambda induction is not elevated during the growth of E. coli (lambda) (RP4::D3112) cells at 30 degrees C. The character of the TCS phenotype was not affected by lex A3 or lex A51 mutations (which cause correspondingly non-inducibility or constitutive expression of the SOS regulon). It was concluded therefore that the TCS phenotype is not related to induction of the SOS response. It was found also that the mutation to heat shock gene dnaJ (dnaJ259) is a cause for significant decrease in phage D3112 production in E. coli dnaJ259 (RP4::D3112) cells. The DNA hybridization data of labelled RP4 and D3112 DNA with total E. coli dnaJ259 (RP4::D3112) DNA suggest that the dnaJ259 probably affected the late D3112 functions.

Bacteriophage lambda↗

PubMed1992

The species concept and its application to tailed phages.

A recently proposed polythetic definition of virus species appears easily applicable to bacteriophages. Criteria for classification of tailed phages are evaluated. Morphology, DNA homology, and serology are the most important criteria for delineation of species, but no single criterion is satisfactory. Dot-blot hybridization and seroneutralization may suggest false relationships by detecting common sequences in the DNA of otherwise unrelated phages. Species of tailed phages can be defined by a combination of morphology and DNA homology or serology. A procedure for identification of novel phages is outlined. Phage names should include elements of host names.

Bacteriophages↗

PubMed1991

[Features of genome expression of phage transposon D3112 of Pseudomonas aeruginosa in Escherichia coli bacteria: dependence of bacterial phenotype on copy number of D3112 genome].

Escherichia coli (RP4 :: D3112) bacteria manifest Tcs phenotype (thirty centigrade sensitivity), i.e. the cells do not divide and form colonies under conditions of lowered temperature (30 degrees C and lower), while cells grow normally at 42 degrees C. In this work it is demonstrated that replication-transposition of D3112 and the Tcs phenotype depend on no recA system of E.coli. Following events lead to the loss of the Tcs phenotype (in E.coli (RP4 :: D3112) cells survived after growing at 30 degrees C): occurrence of mutations in bacterial, phage and plasmid genomes, elimination of DNA of hybrid plasmid or RP4 DNA (a portion of DNA) as well as integration of the hybrid plasmid into bacterial chromosome. In the latter case, the E.coli (D3112) cells acquired the properties shared by the initial bacteria and those with the Tcs phenotype. Such clones are designated tcl (thirty centigrade low sensitivity), they are able to form colonies at 30 degrees C but their growth is more slow, they maintain instability at lowered temperature and continue to produce D3112 phage. The tcl clones in which replication-transposition of D3112 DNA in less effective than in the tcs clones are a suitable object for the study of genetic rearrangements caused by D3112 phage transposon. It is shown that either complete RP4 genome or its portion are comprised between direct repeats of D3112 and are built into various chromosomal sites, i.e. cointegrates are being formed. Two types of deletions are revealed: eliminating sites of RP4 plasmid adjacent to the left end of D3112 genome as well as deletions of the D3112 genome. It is demonstrated that alteration in the growth nature of E.coli, carrying D3112 DNA, at 30 degrees C depends on the copy number of D3112 per bacterial cell.

Bacteriophages↗

PubMed1991

[A comparative analysis of the action of zootoxins on the isolated heart].

A comparative analysis of cardiotropic activity of toxins has been studied in experiments on isolated heart of the poisonous animals from different systematic groups living on the territory of the USSR: reptiles (the venom of cobra, Vipera lebetina, Ancistrodon blomhoffi), amphibian (the venom of Bufo, Bombina, salamander), arachnids (the venom of Apis, Scolopendra, scorpion). The specific cardiotropic activity of the scorpion and Bufo venom has been discovered. The mechanisms of the cardiostimulative activity of scorpion venom have been found to be due to the activation of cellular adrenoreactive structures, and the Bufo venom to the activation of the intracellular calcium. The prospects of zootoxins using in cardiology for development of cardiotonic drugs and modelling the pathologic states in blood circulation system is substantiated.

Amphibian Venoms↗

PubMed1991

[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.

Bacteriophages↗

PubMed1989

[The effect of the IncP-2-group plasmid on the growth of Pseudomonas aeruginosa bacteriophages].

The influence of plasmids of the IncP-2 group on development of bacteriophages of Pseudomonas aeruginosa was studied. Six different types of phage growth inhibition conferred by natural plasmids of the IncP-2 group were found. All these plasmids were shown to have no effect on adsorption and injection of phage DNA into cells, only blocking intracellular phage development. The differences between phage inhibition mechanisms were shown by comparison of efficiency of colony formation by cells containing different plasmids, in the presence of different phages. The presence of the RpL11 plasmid reduces the frequency of lysogenization with G101 phage but not with B3 phage. The mutants of pMG53 plasmid having modified phage inhibition spectrum were obtained. It was inferred that inhibition of different phages is under control of different loci of this plasmid. The mutants of phage B3 overcoming inhibition by plasmids were obtained. It was supposed that the plasmids act at least at three different sites of the phage B3 genome.

Bacteriophages↗

PubMed1989

[Genetic control of morphogenesis of Pseudomonas aeruginosa transposable phage D3112].

The influence of ts mutations in the early and late genes of transposable phage D3112 on phage morphogenesis was studied. The mutations in the early genes A, B and C were shown to suppress morphogenesis of D3112. Six genes (D, E, F, G, H and I), located from 14 to 29 kbp of the phage physical map, control morphogenesis of phage head. Five genes (J, K, L, M and N), clustered in the 29-36 kbp region of the map, control morphogenesis of tail. The similarity of genetic organization of the Escherichia coli transposable phage Mu and the Pseudomonas aeruginosa phage D3112 is discussed.

Bacteriophages↗

PubMed1989

[Study of morphology and genome structure of Pseudomonas putida bacteriophages for their classification].

A group of 27 bacteriophages specific for Pseudomonas putida strains PpG1 and PpN has been isolated. The phages were characterized and compared with the previously described virulent (pf 16, af, tf and PMW) and temperate (PP56 and PP71) phages. The new phages belong to B1 and C1 morphotypes, according to Ackerman's classification. Phage DNAs were digested with several endonucleases; the molecular weights and homology of the DNAs were determined. All phages of P. putida isolated up to now were distributed into 10 species (groups), on the basis of particle morphology, genome size and the results of homology studies. Recombination processes are believed to participate in formation of phages belonging to certain species.

Bacteriophages↗

PubMed1989

[Integration of phage Mu into the RP4::D3112A-plasmid in Escherichia coli cells].

Hybrid plasmids obtained as a result of Mu phage insertions into the RP4::D3112 plasmid in Escherichia coli cells were studied. Stable maintenance of RP4::D3112 plasmid in E. coli cells was provided by using the D3112 phage genome with a point polar mutation in the A gene which prevented early genes' expression. The presence of D3112A- in the RP4 plasmid has been shown to have no effect on efficiency of phage Mu transposition into this plasmid. Moreover, RP4 and D3112 genomes were equivalent targets for Mu integration. The integration of transposable phage into genome of nonrelated phage can be used as one of the approaches to construct recombinant phage genomes in vivo in the absence of DNA homology.

Coliphages↗

PubMed1988

[Compatibility of transposable phages of Escherichia coli and Pseudomonas aeruginosa. I. Co-development of phages Mu and D3112 and integration of phage D3112 into RP4::Mu plasmid in Pseudomonas aeruginosa cells].

The possibility of using a model system (which included RP4::Mu plasmid and D3112 phage in Pseudomonas aeruginosa cells) for analysis of compatibility of transposable Escherichia coli phage Mu and P. aeruginosa phage D3112, as phages and transposons, was studied. No interaction was observed during the vegetative growth of phages. The majority of the hybrid RP4::Mu plasmids lost the Mu DNA after insertion of D3112 into RP4::Mu. The phenomenon was not a result of transposition immunity. We consider the loss of the Mu DNA as a consequence either of plasmid RP4::Mu instability in P. aeruginosa cells, because of the lack of functional Mu repressor, or of some D3112-encoded activity involved in its transposition. For the inambiguous conclusion on compatibility of two phages as transposons, it is necessary to modify the model system, eliminating the possibility of Mu phage replication--transposition.

Bacteriophages↗

PubMed1988

[Interaction of heterologous bacteriophages: growth suppression of temperate PP56 phage of Pseudomonas putida by the transposable phage D3112 of Pseudomonas aeruginosa].

We have found an inhibiting effect of hybrid RP4::D3112 plasmid (where D3112 is represented as genome of a transposable phage specific for Pseudomonas aeruginosa) on the development of temperate P. putida phage PP56. The study of the effect has revealed a previously unknown locus (in the region 12-14.2 kb of the D3112 genome) which functions in the prophage state. The locus affects PP56 decreasing phage yield. Mutants of PP56 insensitive to inhibition were found.

Bacteriophages↗

PubMed1988

[Minigenomes of the transposable phage D3112 of Pseudomonas aeruginosa and their properties].

Two derivatives of D3112 prophage with large internal deletions (mini-D3112) have been constructed. Mini-D3112 delta H is about 3.5 kb long, containing the repressor c1 gene. Mini-D3112 delta E is about 12 kb long, contains the c1 gene, several structural genes and replication gene A. These mini-D3112 are unable to replicate. However, they could replicate and maturated in the presence of the helper D3112cts. Mini-D3112 mediate translocation of the gene argH from the chromosome into the R' plasmids, the translocated fragment being sandwiched between two mini-D3112 genomes.

Bacteriophages↗

PubMed1988

[Transcription of the genome of Pseudomonas aeruginosa phage-transposon D3112 in an homologous host].

In vivo transcription of Pseudomonas aeruginosa transposable phage D3112 was studied. The 3H-labelled RNA isolated from the lysogenic cells PAO1 (D3112cts) after heat induction was hybridized with D3112 DNA to estimate phage-specific RNA. Two main stages of D3112 transcription, including transcription of the early (first 6-8 min) and the late (after 8th min) genes, were revealed. The transcription rate of D3112 early genes achieves the maximum at 3-5 min, being reduced to the minimum at 6-8 min after heat induction. These data point to the existence of negative regulation of D3112 early genes' transcription. The influence of ts mutations in early A, B and C genes and in late ts25 gene on transcription of D3112 phage was studied. It is shown that the genes A and B have no effect on the late transcription, while gene C regulates transcription of the D3112 late genes.

Bacteriophages↗

PubMed1988

[Genetic map of the transposable phage D3112 of Pseudomonas aeruginosa].

Using a large group of newly isolated deletion mutants of prophage D3112 the location of all known mutations of D3112 phage was more precisely defined. The mutations affecting establishment of lysogenic state were mapped in two regions of the genome- 0-1.3 and 29-30 kb. The replicative A gene is mapped between 1.3 and 4.9 kb, the second replicative B gene being situated on the right of the A gene, between 4.9 and 9.4 kb. The C gene which is responsible for positive regulation of phage late genes' expression is mapped within the 9-12 kb region. It is suggested that promoter of the gene C is situated within the same interval. Mutations were isolated in the Lys gene which is responsible for host cell lysis. The gene is located within the interval 14-22 kb of the physical map. The order of morphogenetic genes in the late genome region was also established.

Bacteriophages↗

PubMed1988

[Isolation and comparative characteristics of 2 unrelated temperate phages of Pseudomonas putida PpG1].

Two temperate bacteriophages, PP56 and PP71, specific for bacteria of Pseudomonas putida strain PpG1 have been isolated for the first time. Characterization of the phages was performed. Both of them accomplish stable lysogenization of P. putida PpG1 cells. The phages are inducible. Several groups of clear plaque (c) mutants of PP56 and PP71 with altered processes of establishment and maintenance of lysogenic state have been isolated, according to complementation test. The phages differ in following characters: 1) in morphology of mature phage particles (C and B types, according to Bradley classification); 2) in sizes and genome organizations: DNA of PP56 is permuted (up to 30%), its size is 45 kb, the size of terminal redundancy being 2.5 kb; there is no permutation in PP71 DNA of 48 kb and it has "cohesive" ends; 3) no DNA/DNA homology is shown in tests between PP56 and PP71 DNAs. All the data obtained permitted to consider the phages PP56 and PP71 to belong to different unrelated species (families).

Bacteriophages↗

PubMed1988

[Bacteriophages of Pseudomonas putida containing single-stranded canonical DNA breaks].

It was shown that bacteriophage tf as well as bacteriophages phi p4/40, phi p25/42, phi p23/40 and phi p6/40, which are specific to different P. putida strains, contain the single strand breaks in their DNA. The breaks are localized in one strand of DNA molecules and are repairable with T4 DNA ligase. Bacteriophage tf has no detectable DNA homology with phi p4/40, phi p25/42, phi p23/40 and phi p6/40 bacteriophages. All the phages studied have no relation with other known Pseudomonas phages. Bacteriophages phi p4/40 and phi p25/42 share the extensive DNA homology.

Bacteriophages↗

PubMed1988

[Physical map of the DNA of bacteriophage tf of Pseudomonas putida].

A physical map has been constructed for P. putida bacteriophage tf DNA containing single-strand breaks (nicks). Localization of cleavage sites for EcoRI, HindIII, HpaI ClaI, BamHI, SalI, XbaI and XhoI restriction endonucleases was determined. Position of single-strand breaks was mapped by electrophoretic analysis of denatured tf DNA and electron microscopy of partially denatured DNA samples. The tf genome is characterized by the presence of two classes of nicks differing in the frequency of their presence in population of bacteriophage DNA molecules.

Bacteriophages↗

PubMed1986

[Two loci in the genome of the transposable phage B39 of Pseudomonas aeruginosa affecting the process of integration. I. Study of the properties of phages with the Pde- phenotype and mapping of the rms site].

Mutants and recombinants of transposable Pseudomonas aeruginosa bacteriophage B39 with a specific phenotype Pde- (pleiotropic developmental effect) were studied. Pde- phages produce clear minute plaques on lawns of P. aeruginosa PAO1 and fail to grow in cells of PAO1 harbouring Rms 163 (Inc P5) plasmid. Pde+ character is under control of the two loci in phage genome which were designated pdeX and pdeY. In hybrid phages the pdeX and pdeY loci originating from different transposable phages (pdeX from B39 and pdeY from PH132) do not accomplish their function and, as a result, the hybrid phages have the Pde- phenotype. The frequency of integration (f.o.i.) of Pde- phages into bacterial chromosome is lower than f.o.i. for Pde+ phages, as well as the frequency of stable lysogenization of infected bacteria; lytic development of the Pde- phages is also limited. The great difference among the transposable phages in their reaction to the presence of Rms163 plasmid is caused by some differences in the specific rms site in the phage genome. The site is located inside the interval 1.1-3.9 kb of the physical genome map, being closely linked to cI gene of phage B39. The growth of Pde- phages in cells with Rms163 can be restored, due to additional mutations in phage genes affecting lysogenization.

Bacteriophages↗