scholarly journals Adsorption of Extracellular Chromosomal DNA and Its Effects on Natural Transformation of Azotobacter vinelandii

2010 ◽  
Vol 76 (13) ◽  
pp. 4179-4184 ◽  
Author(s):  
Nanxi Lu ◽  
Julie L. Zilles ◽  
Thanh H. Nguyen
Keyword(s):  
Natural Transformation ◽  
Azotobacter Vinelandii ◽  
Soil Surface ◽  
Extracellular Dna ◽  
Chromosomal Dna ◽  
Dna Adsorption ◽  
Silica Surfaces ◽  
Rigid Conformation ◽  
Coated Surface ◽  
Coated Surfaces

ABSTRACT To better understand the influence of environmental conditions on the adsorption of extracellular chromosomal DNA and its availability for natural transformation, the amount and conformation of adsorbed DNA were monitored under different conditions in parallel with transformation assays using the soil bacterium Azotobacter vinelandii. DNA adsorption was monitored using the technique of quartz crystal microbalance with dissipation (QCM-D). Both silica and natural organic matter (NOM) surfaces were evaluated in solutions containing either 100 mM NaCl or 1 mM CaCl2. The QCM-D data suggest that DNA adsorbed to silica surfaces has a more compact and rigid conformation in Ca2+ solution than in Na+ solution and that the reverse is true when DNA is adsorbed to NOM surfaces. While the amounts of DNA adsorbed on a silica surface were similar for Ca2+ and Na+ solutions, the amount of DNA adsorbed on an NOM-coated surface was higher in Ca2+ solution than in Na+ solution. Transformation frequencies for dissolved DNA and DNA adsorbed to silica and to NOM were 6 × 10−5, 5 × 10−5, and 2.5 × 10−4, respectively. For NOM-coated surfaces, transformation frequencies from individual experiments were 2- to 50-fold higher in the presence of Ca2+ than in the presence of Na+. The results suggest that groundwater hardness (i.e., Ca2+ concentration) will affect the amount of extracellular DNA adsorbed to the soil surface but that neither adsorption nor changes in the conformation of the adsorbed DNA will have a strong effect on the frequency of natural transformation of A. vinelandii.

scholarly journals Chlamydia trachomatis intra-bacterial and total plasmid copy number in clinical urogenital samples

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. A. M. C. Dirks ◽  
K. Janssen ◽  
C. J. P. A. Hoebe ◽  
T. H. B. Geelen ◽  
M. Lucchesi ◽  
...  
Keyword(s):  
Chlamydia Trachomatis ◽  
Diagnostic Value ◽  
Plasmid Copy Number ◽  
Extracellular Dna ◽  
Chromosomal Dna ◽  
Plasmid Copy ◽  
Clinical Sensitivity ◽  
Copy Numbers ◽  
Vaginal Swabs ◽  
And Gender

AbstractChlamydia trachomatis (CT) increases its plasmid numbers when stressed, as occurs in clinical trachoma samples. Most CT tests target the plasmid to increase the test sensitivity, but some only target the chromosome. We investigated clinical urogenital samples for total plasmid copy numbers to assess its diagnostic value and intra-bacterial plasmid copy numbers to assess its natural variation. Both plasmid and chromosome copies were quantified using qPCR, and the plasmid:chromosome ratio (PCr) calculated in two cohorts: (1) 383 urogenital samples for the total PCR (tPCr), and (2) 42 vaginal swabs, with one half treated with propium-monoazide (PMA) to prevent the quantification of extracellular DNA and the other half untreated to allow for both tPCr and intra-bacterial PCr (iPCr) quantification. Mann–Whitney U tests compared PCr between samples, in relation to age and gender. Cohort 1: tPCr varied greatly (1–677, median 16). Median tPCr was significantly higher in urines than vaginal swabs (32 vs. 11, p < 0.001). Cohort 2: iPCr was more stable than tPCr (range 0.1–3 vs. 1–11). To conclude, tPCr in urogenital samples was much more variable than previously described. Transport time and temperature influences DNA degradation, impacting chromosomal DNA more than plasmids and urine more than vaginal samples. Data supports a plasmid target in CT screening assays to increase clinical sensitivity.

scholarly journals Anti-Thrombin, Anti-Adhesive, Anti-Migratory, and Anti-Proliferative Activities of Sulfated Galactans from the Tropical Green Seaweed, Udotea flabellum

Marine Drugs ◽  
2018 ◽  
Vol 17 (1) ◽  
pp. 5 ◽  
Author(s):  
Maxsuell Mendes Marques ◽  
Fernando Presa ◽  
Rony Viana ◽  
Mariana Costa ◽  
Monica Amorim ◽  
...  
Keyword(s):  
Antitumor Agents ◽  
Anticoagulant Activity ◽  
Sulfated Polysaccharide ◽  
Northeastern Brazil ◽  
Sulfated Galactans ◽  
Green Seaweed ◽  
Coated Surface ◽  
Time Test ◽  
Coated Surfaces

In this study, sulfated polysaccharide-rich extracts were isolated from 22 tropical seaweeds (4 red, 11 brown, and 7 green) found in northeastern Brazil, and evaluated for the role of anticoagulant agents. Fifteen of the extracts showed anticoagulant activity, including all the extracts from green seaweeds. Udotea flabellum (a green seaweed) extract was the most potent, requiring an amount of only 3 µg to double the plasma coagulation time in the activated partial thromboplastin time test. A similar result was obtained with 1 µg of heparin. Two sulfated homogalactans with anticoagulant activity, F-I (130 kDa) and F-II (75 kDa), were isolated from this extract using several bio-guided purification steps. Their anticoagulant activity, as well as properties related to antitumor activity (anti-proliferative, anti-adhesive, and anti-migratory), were accessed. Their anticoagulant activities were close to that of heparin. We found that F-I and F-II (0.5–10 μg/mL) were not able to directly inhibit thrombin. In the presence of anti-thrombin, F-I (0.5 μg/mL) was more effective than heparin (0.5 μg/mL) in inhibiting thrombin, while F-II showed similar effects as heparin. F-I and F-II also inhibited B16-F10 (murine melanoma cells) adhesion, migration, and proliferation on a fibronectin-coated surface, but not on laminin- or collagen I-coated surfaces. Except for the antiproliferative activity, the other effects of F-I and F-II were eliminated upon their desulfation (~50%), indicating that the degree of sulfation is not as important for F-I and F-II anti-proliferative activity as the sulfation position. Taken together, the results provide strong evidence for the potential utility of sulfated galactans from U. flabellum, making these compounds an interesting option for future investigations that aim to design new anticoagulant/antitumor agents.

Condensation of Low-Surface-Tension Fluids on Microstructured Surfaces at Low Temperature

2017 ◽  
Author(s):  
Abulimiti Aili ◽  
Qiaoyu Ge ◽  
TieJun Zhang
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Low Temperature ◽  
High Surface ◽  
Condensation Heat Transfer ◽  
Lubricant Oil ◽  
Microstructured Surfaces ◽  
Performance Deterioration ◽  
Coated Surface ◽  
Coated Surfaces

Filmwise condensation of a low surface tension fluid (i.e. refrigerant) on microstructured aluminum surfaces is studied to investigate the effect of the structures on condensation heat transfer at low temperature. The hypothesis is that the structures may cause thinning of the condensate film at micro-scales, thus resulting in an enhancement of condensation heat transfer. However, the structures may also decrease the mobility of the condensate near the surface due to increased friction, thus potentially leading to performance deterioration. The aim of this work is to investigate which of the two counteracting mechanisms dominate during filmwise condensation. Condensation experiments are carried out in a low-temperature vacuum chamber. Compared with the Nusselt model of condensation, the microstructured surfaces, either coated or uncoated, show similar performance, with potentially slight enhancement at low subcooling degree and slight deterioration at high subcooling degree. When the microstructured and silane-coated surface is infused with a non-volatile and very low-surface-tension lubricant oil, the lubricant is displaced by the condensate and there is almost no change in the condensation performance. Our results show that, unlike the case of dropwise condensation of high-surface tension fluids, microstructured and coated surfaces with/without infusing oil is not exciting to enhanced filmwise condensation of low-surface-tension fluids.

scholarly journals Fc receptor modulation in mononuclear phagocytes maintained on immobilized immune complexes occurs by diffusion of the receptor molecule.

1983 ◽  
Vol 157 (6) ◽  
pp. 2121-2139 ◽  
Author(s):  
J Michl ◽  
M M Pieczonka ◽  
J C Unkeless ◽  
G I Bell ◽  
S C Silverstein
Keyword(s):  
Plasma Membrane ◽  
Protein Biosynthesis ◽  
Fc Receptor ◽  
Mononuclear Phagocytes ◽  
Receptor Modulation ◽  
Igg Binding ◽  
Mouse Macrophages ◽  
Coated Surface ◽  
Coated Surfaces ◽  
Antigen Antibody

We describe a method for synchronously assembling antigen-antibody complexes underneath macrophages adherent to an antigen-coated surface. We have used this method to study the mechanism of Fc receptor (FcR) disappearance that occurs when resident and thioglycollate-elicited mouse macrophages are cultured on immune complex-coated surfaces. Erythrocytes opsonized with IgG (E(IgG) and a monoclonal antibody (2.4G2 IgG) directed against the trypsin-resistant FcR (FcRII) were used as indicators of the presence and distribution of FcRII molecules on the macrophage plasma membrane. Inhibitors of aerobic (NaCN) and anerobic (2-deoxyglucose, NaF) glycolysis and pinocytosis, of protein biosynthesis (cycloheximide), and of cytoskeletal function (cytochalasin B and D, colchicine, podophyllotoxin, taxol) did not reduce the rate or extent of FcRII modulation. Moreover, treatment of the macrophages with 0.1-0.5% formaldehyde did not reduce the extent of FcRII modulation as measured by the disappearance of E(IgG) binding sites. FcRII modulation was markedly slowed when the temperature was decreased to 2-4 degrees C. These results prove that FcRII modulation is governed by diffusion of the receptor in the plasma membrane. From the speed of FcRII disappearance from the macrophage's upper surface we calculate that the receptor has a diffusion coefficient at 37 degrees C of 2.5 X 10(-9) cm2/s. This finding indicates that FcRII, in its unligated form, is not linked to the macrophage's cytoskeleton, and that the receptor is capable of accommodating spatially to any distribution of ligands on a particle's surface.

Platelets selectively enhance lymphocyte adhesion on subendothelial matrix under arterial flow conditions

2012 ◽  
Vol 108 (08) ◽  
pp. 328-337 ◽  
Author(s):  
Maria Ersoy ◽  
Paul Hjemdahl ◽  
Naphtali Savion ◽  
David Varon ◽  
Galia Spectre ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
B Cells ◽  
Nk Cells ◽  
Platelet Activation ◽  
Platelet Adhesion ◽  
Nk Cell ◽  
Lymphocyte Adhesion ◽  
Subendothelial Matrix ◽  
Coated Surface ◽  
Coated Surfaces

SummaryPlatelet adhesion at sites of cardiovascular injury may facilitate leukocyte deposition. We asked if and how platelets enhance lymphocyte adhesion on different subendothelial matrix protein (SEMP)-coated surface at arterial shear stress. Hirudinised whole blood was subjected to an arterial shear rate (500 s−1) in a Cone and Plate(let) analyser (CPA) for 5 minutes using plates coated with bovine serum albumin (BSA), collagen, fibrinogen, von Willebrand factor (vWF), or fibronectin. Platelet and lymphocyte adhesion were monitored by CPA and flow cytometry. Exposure of blood to collagen, fibrinogen, and vWF-coated surfaces induced platelet activation. The most marked effect was seen with collagen-coating, which markedly enhanced the adhesion of all lymphocyte subpopulations compared to BSA-coating. Fibrinogen-coating supported both T and NK cell adhesion, while vWF-coated surface only enhanced NK cell deposition. In contrast, fibronectin enhanced neither platelet activation nor lymphocyte adhesion. Moreover, platelets preferentially facilitated adhesion of large CD4+ and CD8+ T cells and NK cells, and of small B cells. Enhanced cell adhesion of larger lymphocytes was associated with elevated platelet conjugation and higher lymphocyte expression of PSGL-1, Mac-1, and CD40L. The enhancement of lymphocyte adhesion was totally platelet-dependent, and was abolished in platelet-depleted blood. Moreover, blockade of the platelet adhesion molecules P-selectin, GPIIb/IIIa, and CD40L attenuated platelet-dependent lymphocyte deposition. In conclusion, platelets support lymphocyte adhesion on SEMP-coated surfaces under arterial shear. The enhancement is selective for large T and NK cells and small B cells.

scholarly journals Natural Transformation of Acinetobactersp. Strain BD413 with Cell Lysates of Acinetobacter sp.,Pseudomonas fluorescens, and Burkholderia cepaciain Soil Microcosms

2000 ◽  
Vol 66 (1) ◽  
pp. 206-212 ◽  
Author(s):  
Kaare M. Nielsen ◽  
Kornelia Smalla ◽  
Jan D. van Elsas
Keyword(s):  
Pseudomonas Fluorescens ◽  
Burkholderia Cepacia ◽  
Natural Transformation ◽  
Bacterial Species ◽  
Physical Stability ◽  
Biological Significance ◽  
Bacterial Cells ◽  
Chromosomal Dna ◽  
Cell Lysates

ABSTRACT To elucidate the biological significance of dead bacterial cells in soil to the intra- and interspecies transfer of gene fragments by natural transformation, we have exposed the kanamycin-sensitive recipient Acinetobacter sp. strain BD413(pFG4) to lysates of the kanamycin-resistant donor bacteria Acinetobacterspp., Pseudomonas fluorescens, and Burkholderia cepacia. Detection of gene transfer was facilitated by the recombinational repair of a partially (317 bp) deleted kanamycin resistance gene in the recipient bacterium. The investigation revealed a significant potential of these DNA sources to transformAcinetobacter spp. residing both in sterile and in nonsterile silt loam soil. Heat-treated (80°C, 15 min) cell lysates were capable of transforming strain BD413 after 4 days of incubation in sterile soil and for up to 8 h in nonsterile soil. Transformation efficiencies obtained in vitro and in situ with the various lysates were similar to or exceeded those obtained with conventionally purified DNA. The presence of cell debris did not inhibit transformation in soil, and the debris may protect DNA from rapid biological inactivation. Natural transformation thus providesAcinetobacter spp. with an efficient mechanism to access genetic information from different bacterial species in soil. The relatively short-term biological activity (e.g., transforming activity) of chromosomal DNA in soil contrasts the earlier reported long-term physical stability of DNA, where fractions have been found to persist for several weeks in soil. Thus, there seems to be a clear difference between the physical and the functional significance of chromosomal DNA in soil.

Radiation Induced Surface Activation on SUS304 Rod Surface Coated With Thin Film Layer Formed by Vacuum Evaporation Method

2008 ◽  
Author(s):  
Jian Zhang ◽  
Kaichiro Mishima ◽  
Naoki Sugitani ◽  
Masahiro Hino ◽  
Tomoji Takamasa
Keyword(s):  
Gamma Ray ◽  
Vacuum Evaporation ◽  
Outer Diameter ◽  
Evaporation Method ◽  
Thin Film Layer ◽  
Radiation Induced ◽  
Gamma Ray Irradiation ◽  
Film Layer ◽  
Coated Surface ◽  
Coated Surfaces

In this study, the effect of film layer deposited on a metal surface by vacuum evaporation method on the RISA phenomenon was investigated from the view points of surface wettability and quenching velocity. Test rods were made of SUS304 with the outer diameter of 24mm and the length of 150mm. Four kinds of materials, i.e. titanium, zircaloy-II, germanium and silicon, were deposited separately on the half-circumference surface of a SUS304 rod with thickness of 200 nm. It was concluded that the RISA effect was observed on the film-coated surfaces after gamma-ray irradiation, which is similar to that on an oxide layer of SUS304 surface. It was also found that the quenching velocity on film-coated surfaces was much faster than that on an un-coated surface.

Experimental Investigation on the Anti-Fouling and Heat Transfer Performance of the Coated Surfaces

2010 ◽  
Author(s):  
Zhi-ming Xu ◽  
Ling Chen ◽  
Ying-lun Gao ◽  
Zhong-bin Zhang
Keyword(s):  
Heat Transfer ◽  
Base Metal ◽  
Heat Transfer Performance ◽  
Solution Concentration ◽  
Solution Temperature ◽  
Transfer Performance ◽  
Characteristic Parameters ◽  
Temperature Solution ◽  
Coated Surface ◽  
Coated Surfaces

The main purpose of this investigation was to study the anti-fouling and heat transfer performance of coated surfaces (ECTFE, FEP, PTFE and PFA). In the present investigation, the heat transfer performance of the coated surfaces was compared to base metal surfaces, and crystallization fouling experiments of coated surfaces were carried out under various operating parameters such as solution temperature, solution concentration and hydrodynamics of the system. The characteristic parameters of the coated surface, such as surface roughness, surface contour, contact angle and surface energy were measured and calculated, which were used to analyze the anti-fouling performances of the coated surface. The results show that compared with the base metal surface, Nusselt number of coated surfaces decrease. But coated surfaces have advantage on anti-fouling ability.

scholarly journals Natural Transformation of Gallibacterium anatis

2012 ◽  
Vol 78 (14) ◽  
pp. 4914-4922 ◽  
Author(s):  
Bodil M. Kristensen ◽  
Sunita Sinha ◽  
John D. Boyce ◽  
Anders M. Bojesen ◽  
Joshua C. Mell ◽  
...  
Keyword(s):  
Bioinformatics Analysis ◽  
Natural Transformation ◽  
Genetic Manipulation ◽  
Targeted Mutagenesis ◽  
Chromosomal Dna ◽  
Natural Competence ◽  
Content Type ◽  
Transformation Procedure ◽  
High Transformation ◽  
Dna Types

ABSTRACTGallibacterium anatisis a pathogen of poultry. Very little is known about its genetics and pathogenesis. To enable the study of gene function inG. anatis, we have established methods for transformation and targeted mutagenesis. The genusGallibacteriumbelongs to thePasteurellaceae, a group with several naturally transformable members, includingHaemophilus influenzae. Bioinformatics analysis identifiedG. anatishomologs of theH. influenzaecompetence genes, and natural competence was induced inG. anatisby the procedure established forH. influenzae: transfer from rich medium to the starvation medium M-IV. This procedure gave reproducibly high transformation frequencies withG. anatischromosomal DNA and with linearized plasmid DNA carryingG. anatissequences. Both DNA types integrated into theG. anatischromosome by homologous recombination. Targeted mutagenesis gave transformation frequencies of >2 × 10−4transformants CFU−1. Transformation was also efficient with circular plasmid containing noG. anatisDNA; this resulted in the establishment of a self-replicating plasmid. Nine diverseG. anatisstrains were found to be naturally transformable by this procedure, suggesting that natural competence is common and the M-IV transformation procedure widely applicable for this species. TheG. anatisgenome is only slightly enriched for the uptake signal sequences identified in other pasteurellaceaen genomes, butG. anatisdid preferentially take up its own DNA over that ofEscherichia coli. Transformation by electroporation was not effective for chromosomal integration but could be used to introduce self-replicating plasmids. The findings described here provide important tools for the genetic manipulation ofG. anatis.

scholarly journals comH, a Novel Gene Essential for Natural Transformation of Helicobacter pylori

2000 ◽  
Vol 182 (14) ◽  
pp. 3948-3954 ◽  
Author(s):  
Leonard C. Smeets ◽  
Jetta J. E. Bijlsma ◽  
Sacha Y. Boomkens ◽  
Christina M. J. E. Vandenbroucke-Grauls ◽  
Johannes G. Kusters
Keyword(s):  
Helicobacter Pylori ◽  
Natural Transformation ◽  
Bacterial Genome ◽  
Uptake System ◽  
Dna Uptake ◽  
Mutant Library ◽  
Chromosomal Dna ◽  
Orthologous Genes ◽  
Helicobacter Felis ◽  
H Pylori

ABSTRACT Helicobacter pylori is naturally competent for transformation, but the DNA uptake system of this bacterium is only partially characterized, and nothing is known about the regulation of competence in H. pylori. To identify other components involved in transformation or competence regulation in this species, we screened a mutant library for competence-deficient mutants. This resulted in the identification of a novel,Helicobacter-specific competence gene (comH) whose function is essential for transformation of H. pyloriwith chromosomal DNA fragments as well as with plasmids. Complementation of comH mutants in transcompletely restored competence. Unlike other transformation genes ofH. pylori, comH does not belong to a known family of orthologous genes. Moreover, no significant homologs ofcomH were identified in currently available databases of bacterial genome sequences. The comH gene codes for a protein with an N-terminal leader sequence and is present in both highly competent and less-efficient transforming H. pyloristrains. A comH homolog was found in Helicobacter acinonychis but not in Helicobacter felis andHelicobacter mustelae.

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