Critical behaviour pervades scientific disciplines as diverse as geology, economy or sociology. The critical behaviour of cell control systems is an open issue whose role has not yet been fully explored. The control of the expression of lambda phage DNA in the host cell can be classified as a system with critical behaviour. Lambda phage is a virus that infects Escherichia coli. Its core genes maintain one of two states; lysogeny or lysis. Current knowledge of the lambda phage genetic network allows to build a computational model of transcriptional control of the genes involved in the lytic-lysogenic switch and to simulate the temporal changes of their expression. Here, we focused on the computational simulation of these gene expressions to demonstrate critical behaviour of the system.
Forty strains of Salmonella enterica (S. enterica) subspecies salamae (II), arizonae (IIIa), diarizonae (IIIb), and houtenae (IV) were isolated from human or environmental samples and tested for bacteriophage production. Production of bacteriophages was observed in 15 S. enterica strains (37.5%) belonging to either the subspecies salamae (8 strains) or diarizonae (7 strains). Activity of phages was tested against 52 pathogenic S. enterica subsp. enterica isolates and showed that phages produced by subsp. salamae had broader activity against pathogenic salmonellae compared to phages from the subsp. diarizonae. All 15 phages were analyzed using PCR amplification of phage-specific regions and 9 different amplification profiles were identified. Five phages (SEN1, SEN4, SEN5, SEN22, and SEN34) were completely sequenced and classified as temperate phages. Phages SEN4 and SEN5 were genetically identical, thus representing a single phage type (i.e. SEN4/5). SEN1 and SEN4/5 fit into the group of P2-like phages, while the SEN22 phage showed sequence relatedness to P22-like phages. Interestingly, while phage SEN34 was genetically distantly related to Lambda-like phages (Siphoviridae), it had the morphology of the Myoviridae family. Based on sequence analysis and electron microscopy, phages SEN1 and SEN4/5 were members of the Myoviridae family and phage SEN22 belonged to the Podoviridae family.
- MeSH
- DNA virů genetika izolace a purifikace MeSH
- druhová specificita MeSH
- elektronová mikroskopie MeSH
- fágy salmonel klasifikace izolace a purifikace fyziologie ultrastruktura MeSH
- fylogeneze MeSH
- genom virový MeSH
- lyzogenie MeSH
- mikrobiologie životního prostředí MeSH
- Salmonella enterica izolace a purifikace virologie MeSH
- salmonelóza mikrobiologie MeSH
- sekvenční analýza DNA MeSH
- sekvenční homologie nukleových kyselin MeSH
- virová nálož MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
- Geografické názvy
- Československo MeSH
In Staphylococcus aureus, generalized transduction mediated by temperate bacteriophages represents a highly efficient way of transferring antibiotic resistance genes between strains. In the present study, we identified and characterized in detail a new efficiently transducing bacteriophage of the family Siphoviridae, designated ϕJB, which resides as a prophage in the meticillin-resistant S. aureus (MRSA) strain Jevons B. Whole-genome sequencing followed by detailed in silico analysis uncovered a linear dsDNA genome consisting of 43 ,12 bp and comprising 70 ORFs, of which ∼40 encoded proteins with unknown function. A global genome alignment of ϕJB and other efficiently transducing phages ϕ11, ϕ53, ϕ80, ϕ80α and ϕNM4 showed a high degree of homology with ϕNM4 and substantial differences with regard to other phages. Using a model transduction system with a well-defined donor and recipient, ϕJB transferred the tetracycline resistance plasmid pT181 and a penicillinase plasmid with outstanding frequencies, beating most of the above-mentioned phages by an order of magnitude. Moreover, ϕJB demonstrated high frequencies of transferring antibiotic resistance plasmids even upon induction from a lysogenic donor strain. Considering such transducing potential, ϕJB and related bacteriophages may serve as a suitable tool for elucidating the nature of transduction and its contribution to the spread of antibiotic resistance genes in naturally occurring MRSA populations.
- MeSH
- aktivace viru MeSH
- bakteriální léková rezistence MeSH
- DNA virů chemie genetika MeSH
- fylogeneze MeSH
- genom virový MeSH
- lyzogenie MeSH
- methicilin rezistentní Staphylococcus aureus virologie MeSH
- molekulární sekvence - údaje MeSH
- otevřené čtecí rámce MeSH
- plazmidy MeSH
- pořadí genů MeSH
- přenos genů horizontální MeSH
- profágy genetika izolace a purifikace ultrastruktura MeSH
- sekvenční analýza DNA MeSH
- sekvenční homologie MeSH
- Siphoviridae genetika izolace a purifikace ultrastruktura MeSH
- syntenie MeSH
- transdukce genetická * MeSH
- transmisní elektronová mikroskopie MeSH
- výpočetní biologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The transduction mediated by bacteriophages is considered to be one of the primary driving forces in horizontal gene transfer in staphylococci, which is crucial to their adaptation and successful evolution. For a transduction to be effective, it is generally accepted that the recipient strain should be susceptible to the transducing phage. In this study, we demonstrate that the plasmid DNAs are effectively transduced into the recipient Staphylococcus aureus strains in spite of their insensitivity to the lytic action of the transducing phage, provided that these phages adsorb effectively to the bacterial cells. The tetracycline and penicillinase plasmids were transduced to insensitive laboratory and clinical strains by bacteriophages ϕ29, ϕ52A and ϕ80α as well as by prophage ϕ53 and naturally occurring prophages induced from donor lysogenic strains. Comparable frequencies of transduction were achieved in both phage-sensitive and phage-insensitive recipient strains. We have demonstrated that such mechanisms as the restriction of DNA and lysogenic immunity which are responsible for insensitivity of cells to phages may not be a barrier to the transfer, maintenance and effective spread of plasmids to a wider range of potential recipients in the staphylococcal population.
- MeSH
- antibakteriální látky farmakologie MeSH
- lyzogenie MeSH
- mnohočetná bakteriální léková rezistence MeSH
- penicilinasa genetika MeSH
- plazmidy * MeSH
- profágy genetika fyziologie MeSH
- stafylokokové bakteriofágy genetika fyziologie MeSH
- stafylokokové infekce mikrobiologie MeSH
- Staphylococcus aureus genetika virologie MeSH
- tetracyklin farmakologie MeSH
- transdukce genetická * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Coevolution between bacteria and bacteriophages can be characterized as an infinitive constant evolutionary battle (phage-host arm race), which starts during phage adsorption and penetration into host cell, continues during phage replication inside the cells, and remains preserved also during prophage lysogeny. Bacteriophage may exist inside the bacterial cells in four forms with different evolutionary strategies: as a replicating virus during the lytic cycle, in an unstable carrier state termed pseudolysogeny, as a prophage with complete genome during the lysogeny, or as a defective cryptic prophage. Some defensive mechanisms of bacteria and virus countermeasures are characterized, and some evolutionary questions concerning phage-host relationship are discussed.
Large Enterococcus faecalis F4 bacteriophage (described earlier) consisting of double-stranded linear DNA of approximately 60 kb was characterized. Library was prepared of its random DNA fragments and selected recombinants were sequenced. Three phage essential genes were characterized: DNA polymerase, replicative DNA helicase and a minor capsid protein, showing only limited homology to other known phage encoded genes. The occurrence of these genes among enterococci was determined by PCR method. Only two out of 40 tested isolates possessed all three genes, another three isolates contained at least one of the genes, demonstrating low frequency F4 lysogens among natural enterococcal isolates.
Various processes of bacteriophage lambda development in Escherichia coli cells bearing either the whole lambda exo-xis region (with truncated, thus nonfunctional, exo and xis genes) or particular genes from this region were investigated. The presence of either the exo-xis region or the ea8.5 gene on a plasmid resulted in formation of fuzzy plaques by infecting phage. Both efficiency of plating and efficiency of lysogenization were decreased in such hosts. On the other hand, neither the efficiency of adsorption nor intracellular lytic development of the infecting phage (measured in one-step-growth experiments) was affected while significantly more host cells survived the infection, when containing the exo-xis region. Although no effects of the exo-xis region on the activity of the p (L) promoter was detected, this region contributed to a decreased transcription from the cII-stimulated promoters p (I), p (aQ) and p (E). These results, together with the results of measurement of efficiency of plating of phages bearing mutations in cI, cII and cIII genes on hosts containing the exo-xis region, strongly suggest that genes from this region (especially ea8.5) are involved in the regulation of bacteriophage lambda development at the stage of the lysis-vs.-lysogenization decision.
- MeSH
- bakteriofág lambda fyziologie genetika růst a vývoj MeSH
- bakteriolýza MeSH
- DNA-nukleotidyltransferasy genetika chemie MeSH
- Escherichia coli virologie MeSH
- exodeoxyribonukleasy genetika chemie MeSH
- lyzogenie MeSH
- mutace MeSH
- plakové testy MeSH
- regulace exprese virových genů MeSH
- virové proteiny genetika chemie metabolismus MeSH
Striking differences in the production of specific inhibitory agents affecting other strains of the same (or of related) species were found between genera of the family Enterobacteriaceae. We tested 50-163 strains each of the potentially pathogenic genera: Escherichia, Citrobacter, Enterobacter, Kluyvera, and Leclercia for their ability to produce bacteriophages, high-molecular-weight (HMW) and low-molecular-weight (LMW) bacteriocins and siderophores against the same sets of strains, using the cross-test method. The genus Escherichia differs substantially from all other Enterobacteriaceae, harboring a notable proportion of lysogenic (36.6%) and colicinogenic (13.9%) strains. Only 18.2% of the Citrobacter strains are lysogenic and only rarely are they colicinogenic, although in 7.3%, they produce phage tail-like bacteriocins. On the other hand, Kluyvera strains were only in 1.8% lysogenic, no colicinogenic strains were found, but in 7.3%, they produced siderophores causing zones of growth inhibition in agar cultures of strains of the same genus. In Leclercia, 10.0% of the strains were lysogenic, 2.0% produced HMW bacteriocins, no colicinogenic strains were found and 2.0% produced siderophores. Enterobacter has shown 23.1% of strains producing siderophores, whereas merely 7.7% were lysogenic, 1.9% colicinogenic and 3.8% formed phage tail-like bacteriocins. HMW bacteriocins of Enterobacter strains disposed of an unusually wide spectrum of activity. The siderophore activity spectrum was rather wide in any genus, but the siderophores were usually not produced by strains producing phages or colicins.
- MeSH
- antibakteriální látky biosyntéza MeSH
- bakteriociny biosyntéza MeSH
- bakteriofágy fyziologie MeSH
- Enterobacteriaceae klasifikace metabolismus virologie MeSH
- financování organizované MeSH
- incidence MeSH
- koliciny metabolismus MeSH
- kultivační média MeSH
- lidé MeSH
- lyzogenie MeSH
- molekulová hmotnost MeSH
- siderofory metabolismus MeSH
- Check Tag
- lidé MeSH
The entire double-stranded DNA genome of the Streptomyces aureofaciens phage mu1/6 was sequenced and analyzed. Its size is 38.194 kbp with an overall molar G+C content of 71.2 %. Fifty-two potential open reading frames (orfs) were identified, divided into two oppositely transcribed regions. In the left arm of the mu1/6 genome, an identified putative integrase and possible regulation proteins were identified. The rightwards transcribed region contains genes organized into apparently four functional units responsible for: (i) replication, (ii) DNA packaging and head assembly, (iii) tail morphogenesis, and (iv) lysis. Putative functions were assigned to twelve orfs based on bioinformatic analysis or experimental substantiation. Comparative analysis with three complete genomes of streptomycete phages revealed resemblance with respect to the organization of their genes into functional modules. Closer relationship was observed only between mu1/6 and S. venezuelae phage VWB.
- MeSH
- bakteriofágy genetika imunologie MeSH
- finanční podpora výzkumu jako téma MeSH
- genomová knihovna MeSH
- komponenty genomu genetika MeSH
- lyzogenie genetika MeSH
- otevřené čtecí rámce genetika MeSH
- Siphoviridae genetika izolace a purifikace MeSH
- Streptomyces aureofaciens genetika izolace a purifikace MeSH
- tetracyklin farmakologie izolace a purifikace MeSH
- MeSH
- Enterobacteriaceae klasifikace patogenita MeSH
- koliciny analýza biosyntéza MeSH
- lyzogenie fyziologie MeSH
- Publikační typ
- kongresy MeSH
