PubMed Health⌕ Search

Biomedical subjects

V N Krylov

Publications and source records attributed to V N Krylov.

At least 19 recordsLinked to original sources
PubMed2006

[Genome conservatism of phiKMV-like bacteriophages (T7 supergroup) active against Pseudomonas aeruginosa].

The T7-like phiKMV bacteriophage active on Pseudomonas aeruginosa was previously isolated by us and shown to have DNA resistant to many endonucleases. A loss of sensitive sites might be a consequence of a long phiKMV evolution on different hosts. To elucidate, whether this trait is shared by other similar phages, several new phiKMV-like phages were isolated from different sources and compared. All studied phiKMV-like phages formed three groups, insignificantly differing in the number and localization of endonuclease-sensitive DNA sites. This confirms that the present-day phages of this species have highly conserved genomes. Mutational "restoration" of the lost sites may be restricted by a lethal effect. The phiKMV-like phages were shown for the first time to increase the rate of in vitro accumulation of giant phiKZ-like phages of P. aeruginosa. This effect is characteristic only of phiKMV-like phages.

Bacteriophage Typing↗
PubMed2006

[Ambivalent bacteriophages of different species active on Escherichia coli K12 and Salmonella sps. strains].

A study was made of several bacteriophages (including phages U2 and LB related to T-even phages of Escherichia coli) that grow both on E. coli K12 and on some Salmonella strains. Such phages were termed ambivalent. T-even ambivalent phages (U2 and LB) are rare and have a limited number of hosts among Salmonella strains. U2 and LB are similar to canonical E. coli-specific T-even phages in morphological type and size of the phage particle and in reaction with specific anti-T4 serum. Phages U2 and LB have identical sets of structural proteins, some of which are similar in size to structural proteins of phages T2 and T4. DNA restriction patterns of phages U2 and LB differ from each other and from those of T2 and T4. Still, DNAs of all four phages have considerable homology. Unexpectedly, phages U2 and LB grown on Salmonella bungori were unstable during centrifugation in a CsCl gradient. Ambivalent bacteriophages were found in species other than T-even phages and were similar in morphotype to lambdoid and other E. coli phages. One of the ambivalent phages was highly similar to well-known Felix01, which is specific for Salmonella. Ambivalent phages can be used to develop a new set for phage typing in Salmonella. An obvious advantage is that ambivalent phages can be reproduced in the E. coli K12 laboratory strain, which does not produce active temperate phages. Consequently, the resulting typing phage preparation is devoid of an admixture of temperate phages, which are common in Salmonella. The presence of temperate phages in phage-typing preparations may cause false-positive results in identifying specific Salmonella strains isolated from the environment or salmonellosis patients. Ambivalent phages are potentially useful for phage therapy and prevention of salmonellosis in humans and animals.

Antibodies↗
PubMed2006

[Comparison of new giant bacteriophages OBP and Lu11 of soil pseudomonads with bacteriophages of phiKZ-supergroup of Pseudomonas aeruginosa].

Study of two recently isolated giant bacteriophages Lu11 and OBP that are active on Pseudomonas putida var. Manila and Pseudomonas fluorescens, respectively, demonstrated their similarity in morphology, genome size, and size of phage particles, with giant bacteriophages of Pseudomonas aeruginosa assigned to the supergroup of phiKZ-like phages of the family Myoviridae designated in this manner according to the best studied phage phiKZ that belongs to the species of this group widely distributed in nature. Comparison of major polypeptide sizes of mature particles suggests the similarity of certain proteins in the phages examined. In OBP particles visualized with an electron microscope, an "inner body" was detected, which points to the specific DNA package intrinsic to phages of phiKZ group. In the meantime, phages Lul11 and OBP do not exhibit resemblance among themselves or with any of earlier described phiKZ-like phages in respect to other traits; particularly, they have no detectable DNA homology. Note that phage Lu11 of P. putida var. Manila exhibits very slight homology with phage Lin68 of the family of P. aeruginosa phiKZ-like phages detected only in blot hybridization. This suggests the possible involvement of these phages in interspecies recombination ("gene shuffling") between phages of various bacterial species. Results of partial sequencing of phage genomes confirmed the phylogenetic relatedness of phage OBP to phages of the phiKZ-supergroup, whereas phage Lu11 most probably belongs to a novel species that is not a member of supergroup phiKZ composition. The results of the study are discussed in terms of the evolution of these phages.

Genome, Viral↗
PubMed2005

[Comparison of the genome for phylogenetically related bacteriophages phiKZ and EL of Pseudomonas aeruginosa: evolutionary aspects and minimal genome size].

Bacteriophages of the family Myoviridae represent one of the most widespread domains of the biosphere substantially affecting the ecological balance of microorganisms. Interestingly, sequence analysis of genomic DNAs of large bacteriophages revealed many genes coding for proteins with unknown functions. A new approach is proposed to improve the functional identification of genes. This approach is based on comparing the genome sequence for phylogenetically and morphologically related phages showing no considerable homology at the level of genomic DNA. It is assumed that gene functions essential for the development of phages of a given family are conserved and that the corresponding genes code for similar orthologous proteins even when lacking sequence homology. The genome was sequenced and compared for two Pseudomonas aeruginosa giant bacteriophages, phiKZ and EL, which belong to a group of (phiKZ-related phages. A substantial difference in genome organization was observed, suggesting specific features of phage evolution. In addition, the problem of the minimal genome of the superfamily is discussed on the basis of the difference in size and structure between the phiKZ and EL genomes.

Base Sequence↗
PubMed2004

[Comparison of genomes of new gigantic Pseudomonas aeruginosa phages from native populations from different regions].

To study the genome diversity of bacteriophages from geographically distant natural populations, new giant phi KZ-like Pseudomonas aeruginosa phages isolated in two different regions were compared with earlier known phages of three species (phi KZ, Lin68, EL). A broad spectrum of lytic activity was demonstrated for all phi KZ-like phages. Phages of the phi KZ species proved to be common in natural populations of various regions, while IL- and Lin68-related phages were extremely rare. Most phi KZ-related phages had unique DNA restriction patterns, but the differences between these were only minor, and the genomes did not contain nonhomologous fragments. The spectrum of capsid polypeptides proved to be conserved in each species, and was proposed as a character necessary and sufficient for express classification of phages with an accuracy of species. Phages isolated in different geographical regions showed no substantial difference. Some phages only slightly differing in DNA restriction pattern from phi KZ may be used to study the origin of phi KZ genes coding for orthologs of proteins of unrelated species (other phages, pathogenic bacteria, eukaryotes).

Blotting, Western↗
PubMed2003

[Role of horizontal gene transfer by bacteriophages in the origin of pathogenic bacteria].

The review considers the involvement of bacteriophages in transferring genes, which determine bacterial pathogenicity, and the increasing role of comparative genomics and genetics of bacteria and bacteriophages in detecting new cases of horizontal gene transfer. Examples of phage participation in this process proved to a different extent are described. Emphasis is placed on the original work carried out in Russia and focused on bacteriophages (temperate transposable phages and giant virulent phi KZ-like phages) of conditional pathogen Pseudomonas aeruginosa. Consideration is given to the possible lines of further research of the role of bacteriophages in the infection process and, in particular, the role of virulent phages, whose products are similar to those of pathogenic bacteria, in modification of clinical signs of infectious diseases and in evolution. An attempt is made to predict the possible direction of pathogen evolution associated with development of new treatment strategies and generation of new specific niches.

Animals↗
PubMed2002

[Phenogenetic characterization of a group of giant Phi KZ-like bacteriophages of Pseudomonas aeruginosa].

A comparative study was made of a group of Pseudomonas aeruginosa virulent giant DNA bacteriophages similar to phage phi KZ in several genetic and phenotypic properties (particle size, particle morphology, genome size, appearance of negative colonies, high productivity, broad spectrum of lytic activity, ability to overcome the suppressing effect of plasmids, absence of several DNA restriction sites, capability of general transduction, pseudolysogeny). We have recently sequenced the phage phi KZ genome (288,334 bp) [J. Mol. Biol., 2002, vol. 317, pp. 1-19]. By DNA homology, the phages were assigned to three species (represented by phage phi KZ, Lin68, and EL, respectively) and two new genera (phi KZ and EL). Restriction enzyme analysis revealed the mosaic genome structure in four phages of the phi KZ species (phi KZ, Lin21, NN, and PTB80) and two phages of the EL species (EL and RU). Comparisons with respect to phage particle size, number of structural proteins, and the N-terminal sequences of the major capsid protein confirmed the phylogenetic relatedness of the phages belonging to the phi KZ genus. The origin and evolution of the phi KZ-like phages are discussed. Analysis of protein sequences encoded by the phage phi KZ genome made it possible to assume wide migration of the phi KZ-like phages (wandering phages) among various prokaryotes and possibly eukaryotes. Since the phage phi KZ genome codes for potentially toxic proteins, caution must be exercised in the employment of large bacteriophages in phage therapy.

Biological Evolution↗
PubMed2001

[Phagotherapy in terms of bacteriophage genetics: hopes, perspectives, safety, limitations].

The appearance and spreading of multidrug-resistant bacterial pathogens is a consequence of the large-scale use of antibiotics in medicine. In view of this, claims for the phage therapy were renewed: in recent studies, the natural phages and their products neutralizing various proteins, as well as the bacterial products often controlled by defective prophages (bacteriocins) were applied for treatment of bacterial infections. Constructs obtained by gene engineering are increasingly used to change some bacteriophage: properties to expand the spectrum of their lytic activity and to eliminate therapeutic drawbacks of some natural phages. In this review, the problem of phage therapy is discussed in general with respect to bacteriophage properties, their genetics, structure, evolution, taking into account long-term experience of the author in the field of bacteriophage genetics. Note that the general concept of phage therapy should be developed to ensure long-term, efficient and harmless phage therapy.

Animals↗
PubMed2001

[Autoplaque formation in a Pseudomonas fluorescens strain: phage-like particles and transactivation of the defective phage].

Natural bacteriophages of Pseudomonas fluorescens are rare and its temperate phages have not been described so far. In search for these phages, we have found that one of the P. fluorescens strains forms numerous small transparent autoplaques of different size and shape, which contained material reproducible on the same strains. When centrifuged in a cesium chloride gradient, this material yielded a band in the density zone of about 1.3 g/cm3, where protein components or bacteriophages with a relatively low content of nucleic acid are usually located. In the band material, electron microscopy revealed phagelike particles with empty and mostly undamaged heads and tails carrying in their distal region a formation resembling contracted sheath. DNA isolated from the preparation consisted of two components: a distinct 54-kb fragment, and a diffuse fragment ranging in size from 20 to 9.5 kb. Treatment of the large DNA fragment with various endonucleases yielded 42.2- and 29.5-kb fragments (on average for different endonucleases); whereas the same treatment of the diffuse fragment yielded two- to three distinct fragments with the overall molecular sizes of 8.9 and 6.2 kb (for different nucleases). We have suggested that cells harbor two different genetic elements whose interaction results in the autoplaque appearance and in the formation of negative colonies after infection with the autoplaque material. One of the two elements displays properties of a defective prophage with disturbed DNA synthesis and assembly, whereas the other exhibits the properties of a transposable phage. After complementation or some other interaction between these elements (transactivation, prophage induction caused by repressor inactivation), a bulk of defective phage particles devoid of DNA and a few DNA-containing particles were produced. It remains unclear whether both DNA types are contained in the same or different particles. The phage (or a system of elements) referred to as PT3 is noninducible. The phage mutants forming larger negative colonies (NCs) were also revealed. Some of bacterial mutants resistant to PT3 infection produce the mutant phage with small and turbid NCs. PT3 produces no NCs on the lawns of other strains of the same or other pseudomonade species. This is the first case of describing a natural temperate bacteriophage in P. fluorescens. The two different elements of this phage may represent the same genome of the defective prophage divided into two portions within a bacterial chromosome, each of which is capable of packaging into the phage head.

DNA, Viral↗
PubMed2001

[Features of fatty acid composition of queen bee jelly].

Gas liquid chromatography and chromato-mass-spectrometry were used to study Queen bee jelly fatty acid composition. Trans-10-hydroxy-2-decenoic acid was determined as the mane component of Queen bee jelly fatty acid fraction. Mass-fragmentography GC-MS method was developed for determination of the trace trans-10-hydroxy-2-decenoic acid to authenticate Queen bee jelly in products and BAS.

Animals↗
PubMed2000

[Change in erythrocyte sedimentation during compression and decompression].

It is determined that during compression and decompression of blood and blood suspension the main section plane of naturally sedimented erythrocytes assume virtually vertical position and, therefore, sedimentation rate of erythrocytes rises. Also, following compression blood density in vitro is irreversibly increased. The idea of existence of erythrocyte-bonded gas microcavities is discussed.

Atmospheric Pressure↗
PubMed2000

[Isolation and comparative study of a group of temperate bacteriophages of rhizospheric pseudomonads Pseudomonas putida].

We have isolated several new temperate bacteriophages for rhizosphere pseudomonads Pseudomonas putida. Examination of these phages, along with two previously isolated temperate phages PP56 and PP71 of P. putida PpG1 (biovar A), allowed us to classify them into four species on the basis of DNA cross-homology; relative genomic size; and, to a certain extent, the morphology of phage particles. Two of these species are represented by nonidentical variants. No transposable phages were found among these two new species. Three phage species cause various-types of lysogenic conversion manifested in growth suppression of other phage species. This seems to account for the fact that the temperate phage of rhizosphere pseudomonads are seldom encountered. The new phages described can be used for selection of phage-resistant bacterial forms exhibiting antifungal activity that are commercially produced and used for treatment of seeds of cultivated plants.

DNA, Viral↗
PubMed2000

[Properties of natural interspecific hybrids of transposable phages of Pseudomonas aeruginosa: specific characteristics of phage PL24 transposition].

Properties of natural hybrid transposable phages (TP) of Pseudomonas aeruginosa, including phage PL24 and lysogens for this phage, were studied. PL24 possesses the properties of TP from two previously described groups, B3 and D3112. Its genome, unlike the genome of D3112, contains many sites susceptible to the SalGI restriction endonuclease and possesses no more than 100 nucleotides of bacterial origin located at the left genome end. However, unlike B3, phage PL24 failed to induce auxotrophic mutants upon integration in the bacterial genome. This phage differed from both B3 and D3112 in sensitivity to chloroform treatment. A more detailed examination of a group containing 25 randomly isolated lysogens for phage PL24 revealed previously unknown processes occurring at early stages of bacterial lysogenization. There are at least two different modes of cell lysogenization with phage PL24. In the first case, the emerging lysogens contained a single prophage genome located (in each lysogen) at individual sites. In the second case, polylysogenic bacteria appeared, and, after primary integration of a phage genome, replicative transposition occurred at new sites (often accompanied by the appearance of prophage clusters at these sites). The choice of the mode of lysogenization can be determined both by differences in the physiological state of bacteria and by specific features of phage PL24, which possibly affect the time of repressor accumulation to the concentration sufficient for blocking phage growth or the stability of the lysogenic state.

DNA Transposable Elements↗
PubMed2000

[Transcriptional mapping and study of transcription regulation of the Pseudomonas aeruginosa phage-transposon D3112].

Regulation of transcription was studied in a wild-type transposable phage (TP) D3112 of Pseudomonas aeruginosa and its mutants for different genes. For this purpose, [3H]RNA-DNA hybridization with denatured fragments from various regions of the D3112 genome bound to nitrocellulose filters was used. A transcriptional map of TP D3112 was constructed based on the data obtained. The map comprised six independent transcriptional units corresponding to the modular organization of the phage genome. Only the repressor gene cI was transcribed in the lysogenic state. After repressor thermoinactivation, the cI transcription ceased, and transcription occurred in the same order as the genes (modules) were located on the D3112 phage genetic map (from left to right): cip1 (a negative regulator) and early genes A and B (controlling the replication-transposition of the phage), nonessential genome region, genes C and the locus marked with the ts47 mutation (positive regulators of late gene transcription), the genes of the head morphogenesis, gene c91 (a positive regulator responsible for the lysogenic state), and the genes of the tail morphogenesis. Similarities between nonhomologous TPs D3112 of P. aeruginosa and Mu of Escherichia coli with respect to genetic organization and transcription regulation are discussed.

DNA Transposable Elements↗
PubMed2000

[Phenotypic effect of mutation ts47 in the Pseudomonas aeruginosa phage transposon D3112 on expression of late phage genes].

At nonpermissive temperature (42 degrees C) the ts47 mutation causes substantial abnormalities in the late phase of the phage intracellular development. In these conditions DNA of the D3112 phage is detected both in a free form and integrated into bacterial chromosome. The transcription kinetics in the ts47 mutant at 42 degrees C was indistinguishable from that typical to other early gene mutants (A, B, and C): specifically, the preservation of the first transcription peak along with low activity of late transcription were observed. Similarly to the C gene, the ts47 mutation-carrying locus is involved in regulating the transcription of the D3112 transposable phage late genes. It is suggested that the mechanism underlying the action of the ts47 mutation differs from that of the C gene product. One of the possible explanations is based on the fact that the product of the ts47 locus affects the activity of cellular RNA polymerase via providing more effective recognition of the phage promoters by the RNA polymerase modified with the phage protein C.

DNA Transposable Elements↗