613 research outputs found
Gac two-component system in Pseudomonas syringae pv. tabaci is required for virulence but not for hypersensitive reaction
No full textPseudomonas syringae pv. tabaci 6605 causes wildfire disease on host tobacco plants. To investigate the regulatory mechanism of the expression of virulence, Gac two-Component system-defective mutants, Delta gacA and Delta gacS, and a double mutant, Delta gacA Delta gacS, were generated. These mutants produced smaller amounts of N-acyl homoserine lactones required for quorum sensing, had lost swarming motility, and had reduced expression of virulence-related hrp genes and the algT gene required for exopolysaccharide production. The ability of the mutants to cause disease symptoms in their host tobacco plant was remarkably reduced, while they retained the ability to induce hypersensitive reaction (HR) in the nonhost plants. These results indicated that the Gac two-component system of P. syringae pv. tabaci 6605 is indispensable for virulence on the host plant, but not for HR induction in the nonhost plants.</p
Predicted <i>P</i>. <i>salmonis</i> GacS/GacA-CsrA/CsrB/CsrC regulatory system.
No full textPredicted P. salmonis GacS/GacA-CsrA/CsrB/CsrC regulatory system.</p
Response of Permanent Monitoring Station (PMS) to increased radioactivity level in comparison with thermoluminescent detectors and Gamma Tracer monitor
No full textThermoluminescence dosimetry of liquid 32P sources of variable size and composition
No full textDosimetry of liquid sources was studied in terms of their size and composition, to check how self-absorption of balloon-based intravascular brachytherapy sources may influence doses at a target point.The sources contained aqueous solutions of -phosphate, saline, and iodinated contrast media (0–). Doses were measured in Plexiglas phantoms at radial distance, using miniature flat thermoluminescence detectors.The absolute dose rates measured for 2.0– diameter range increased from 0.25 to 0.43 and were slightly lower than theoretical values. A diameter balloon delivered 0.33, and a ID Plexiglas tube 0.40 . A titanium stent present on the balloon enhanced the dose rate at distance, whereas an one reduced it. The influence of iodine concentration was not very well pronounced.The observed increase of absolute dose rates in the clinically essential range of source diameters is an important parameter for radiotherapy planning
Transuranic isotopes and 90Sr in attic dust in the vicinity of two nuclear establishments in Northern Germany
No full textAttic dust was chosen as the test medium in order to search for traces of man-made bone seeking alpha and beta emitters. The samples were taken from 5 houses in the community of Elbmarsch situated at the river Elbe, adjacent to the Krümmel nuclear power plant and the nuclear research center of Geesthacht. Five houses in other regions of northern Germany were taken as a control. 238Pu, 239,240Pu, 241Am, and 244Cm were measured by alpha spectrometry after chemical separation. Additionally, 241Pu was measured by liquid scintillation spectrometry, and the fission product 90Sr was measured in a separate investigation. All nuclides except 244Cm showed activities above the detection limit in the Elbmarsch samples and an elevated mean concentration compared to the control. It can be concluded from the activity ratio 241Am/239,240Pu that the Elbmarsch contamination cannot be accounted for by the background levels of transuranic nuclides resulting from weapons fallout. The derived release of alpha emitters is assumed to have contributed to the induction of a leukemia cluster in children, which was observed in Elbmarsch between 1990 and 1996
Simultaneous determination of radioactive halogen isotopes and 99Tc
No full textThe purpose of this study was to develop a simplified method for simultaneous determination of radiologically important halogen isotopes and 99Tc from different types of samples like environmental, biological and waste samples. Due to their long half-lives (longer than 105 years) they play important role in the nuclear cycle, especially in environmental monitoring and protection.For a rapid response in the evaluation of 129I, 36Cl and 99Tc contamination levels of these samples it is advantageous to combine the existing individual methods. According to the present procedure, iodine, chlorine and technetium are separated selectively from the same sample aliquot followed by the ß-spectrometry of the purified fractions. Increased sensitivities can be achieved by neutron activation (NA) especially in the case of 129I.Our work intends to solve the problem by combining the well-known hot acidic distillation method for iodine separation with the organic extraction process characteristic for technetium separation. The major objective of the work was to separate the disturbing halides from iodine. For this purpose a selective oxidant was applied.For the sample destruction and fractionated distillation an air flow-through installation was used with hot concentrated sulphuric and nitric acids. The trap for iodine contained 3 M NaOH solution. After iodine separation the trap was exchanged for a new one containing the same solution for trapping chlorine or bromine with an addition of 0.01 M KMnO4 solution as an oxidative agent. As expected, the main part of technetium was contained in the acidic residue after distillation. Tc purification was performed by organic extraction with TBP and TEVA column
Geographical distribution of 90Sr contamination in Poland
No full textThe paper presents results on determination of 90Sr in bilberry and cowberry leaves (Vaccinium myrtillus and Vaccinium vitis-idaea) and the use of these plants as bio-monitors of radiostrontium contamination in Poland. Radiostrontium was determined by mean of liquid scintillation spectrometry preceded by radiochemical separation using Sr-resin and 85Sr tracer. The approximate map of 90Sr contamination of Poland is presented. The activity ratio between 90Sr and obtained earlier data for 137Cs in the same samples is discussed. The enhancement of radiostrontium content observed in northeastern Poland seems to be the trace of hot-particles fallout from initial Chernobyl cloud, which passed over Polish territory toward Scandinavia
Extracellular protease and phospholipase C are controlled by the global regulatory gene gacA in the biocontrol strain Pseudomonas fluorescens CHA0.
No full textPseudomonas fluorescens strain CHA0 protects plants from various root diseases. Antibiotic metabolites synthesized by this strain play an important role in disease suppression; their production is mediated by the global activator gene gacA. Here we show by complementation that the gacA gene is also essential for the expression of two extracellular enzymes in P. fluorescens CHA0: phospholipase C and a 47-kDa metalloprotease. In contrast, the production of another exoenzyme, lipase, is not regulated by the gacA gene. Protease, phospholipase and antibiotics of P. fluorescens are all known to be optimally produced at the end of exponential growth; thus, the gacA gene appears to be a general stationary-phase regulator
Kahekomponentse signaalsüsteemi GacS-GacA mõju mullabakter Pseudomonas putida mutatsioonisagedusele
No full textBakterite elukeskkond on kiirelt muutuv. Keskkonnatingimuste tunnetamiseks on
bakterites signaalsüsteemid, mis vastavalt keskkonnas toimunud muutustele muudavad
bakteriraku füsioloogiat. Gram-negatiivsete bakterite seas on konserveerunud GacS-GacA
kahekomponentne signaalsüsteem. Pseudomonaadides reguleerib GacS-GacA
signaalsüsteem vastusena keskkonnastiimulitele nii sekundaarsete metaboliitide sünteesi,
virulentsust kui biofilmi moodustumist. Lisaks on leitud, et Pseudomonas putida rakkudes
põhjustab gacS-i defektsus mutatsioonisageduse tõusu. Käesoleva töö eesmärk oli leida, kas
sensorvalgu GacS-i efekt mutatsioonisagedusele toimib läbi regulaatorvalgu GacA. Leiti, et P.
putida PaW85 gacS- ning gacA-defektse tüve puhul on suurenenud mutatsioonisagedus
nälgivates rakkudes ning lisaks uuriti mutatsioonisageduse tõusu põhjuseid
A <i>gacA</i> mutation elevated LPS production.
No full text<p>Lipopolysaccharides from the wild type G5 and the <i>gacA</i> mutant G5-6 were extracted using the LPS Extraction Kit (iNtRON Biotechnol. Inc., Japan), followed by 12% Tricine-SDS-PAGE separation after treatment with proteinase K. Lane 1: the wild type G5; Lane 2; the <i>gacA</i> mutant G5-6.</p
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