Search results for "Escher"
showing 10 items of 728 documents
Assessment of Escherichia coli B with enhanced permeability to fluorochromes for flow cytometric assays of bacterial cell function.
2002
Background Flow cytometry has become a choice methodology for microbiological research. However, functional cytometric assays in live bacteria are still limited. This is due, in part, to the cell wall impairing penetration of vital dyes in bacteria, thus imposing permeabilization procedures. These manipulations may affect cell physiology, provoke cell aggregation or lysis, and they are time-consuming. Escherichia coli B strains have been used for mutagenic assays because of an altered lipopolysaccharide that provokes increased membrane permeability. We assessed the use of these strains as possible alternatives for flow cytometric assays to avoid the permeabilization steps. Methods Suspensio…
Damage in Escherichia coli Cells Treated with a Combination of High Hydrostatic Pressure and Subzero Temperature
2007
ABSTRACT The relationship between membrane permeability, changes in ultrastructure, and inactivation in Escherichia coli strain K-12TG1 cells subjected to high hydrostatic pressure treatment at room and subzero temperatures was studied. Propidium iodide staining performed before and after pressure treatment made it possible to distinguish between reversible and irreversible pressure-mediated cell membrane permeabilization. Changes in cell ultrastructure were studied using transmission electron microscopy (TEM), which showed noticeable condensation of nucleoids and aggregation of cytosolic proteins in cells fixed after decompression. A novel technique used to mix fixation reagents with the c…
Superoxide generation by human neutrophils induced by low doses of Escherichia coli hemolysin.
1991
Escherichia coli hemolysin (Hly) was isolated from bacterial culture supernatants by polyethylene glycol precipitation and centrifugation in glycerol density gradients. The toxin preparations contained less than 1 mol of lipopolysaccharide per 10 mol of protein, and they had no fatty acids. The capacity of purified hemolysin to stimulate superoxide anion production in polymorphonuclear leukocytes was monitored kinetically in a lumimeter by using the lucigenin assay and was correlated with the kinetics of transmembrane pore formation. When applied to leukocytes suspended in protein-free buffer, very low concentrations (0.02 to 0.1 HU/ml) of the toxin strongly stimulated the production of sup…
The presence of KCl in the exposure medium strongly influences the mutagenicity of metabolites of polycyclic aromatic hydrocarbons in Escherichia col…
1994
Abstract Previous studies demonstrated that the ion composition of the exposure medium may strongly influence the mutagenicity of many compounds in the liquid preincubation modification of the reversion assay with his − Salmonella typhimurium strains. Similar influences were now observed in the reversion assay with trp − Escherichia coli strain WP2 uvrA . The exposure medium was 8 mM sodium phosphate buffer (pH 7.4), containing no other ions or 125 mM KCl. Omission of KCl resulted in an about 10-fold enhancement of the mutagenic activity of 7-methylbenz[ a ]anthracene 5,6-oxide, but in a strong decrease in the mutagenicity of 1-hydroxymethylpyrene sulphate, close to the limit of detection. …
Transcriptional regulation and energetics of alternative respiratory pathways in facultatively anaerobic bacteria
1998
Abstract The facultatively anaerobic Escherichia coli is able to grow by aerobic and by anaerobic respiration. Despite the large difference in the amount of free energy that could maximally be conserved from aerobic versus anaerobic respiration, the proton potential and Δg ′ Phos are similar under both conditions. O 2 represses anaerobic respiration, and nitrate represses fumarate respiration. By this the terminal reductases of aerobic and anaerobic respiration are expressed in a way to obtain maximal H + e − ratios and ATP yields. The respiratory dehydrogenases, on the other hand, are not synthesized in a way to achieve maximal H + e − ratios. Most of the dehydrogenases of aerobic respirat…
Scorpiand-like azamacrocycles prevent the chronic establishment of Trypanosoma cruzi in a murine model.
2013
Chagas disease is today one of the most important neglected diseases for its upcoming expansion to non-endemic areas and has become a threat to blood recipients in many countries. In this study, the trypanocidal activity of ten derivatives of a family of aza-scorpiand like macrocycles is evaluated against Trypanosoma cruzi in vitro and in vivo murine model in which the acute and chronic phases of Chagas disease were analyzed. The compounds 4, 3 and 1 were found to be more active against the parasite and less toxic against Vero cells than the reference drug benznidazole, 4 being the most active compound, particularly in the chronic phase. While all these compounds showed a remarkable degree …
Evolution of the leucine gene cluster in Buchnera aphidicola: insights from chromosomal versions of the cluster.
2004
ABSTRACT In Buchnera aphidicola strains associated with the aphid subfamilies Thelaxinae, Lachninae, Pterocommatinae, and Aphidinae, the four leucine genes ( leuA , - B , - C , and - D ) are located on a plasmid. However, these genes are located on the main chromosome in B. aphidicola strains associated with the subfamilies Pemphiginae and Chaitophorinae. The sequence of the chromosomal fragment containing the leucine cluster and flanking genes has different positions in the chromosome in B. aphidicola strains associated with three tribes of the subfamily Pemphiginae and one tribe of the subfamily Chaitophorinae. Due to the extreme gene order conservation of the B. aphidicola genomes, the v…
Biomolecule-corona formation confers resistance of bacteria to nanoparticle-induced killing: Implications for the design of improved nanoantibiotics
2018
Abstract Multidrug-resistant bacterial infections are a global health threat. Nanoparticles are thus investigated as novel antibacterial agents for clinical practice, including wound dressings and implants. We report that nanoparticles' bactericidal activity strongly depends on their physical binding to pathogens, including multidrug-resistant primary clinical isolates, such as Staphylococcus aureus , Klebsiella pneumoniae or Enterococcus faecalis . Using controllable nanoparticle models, we found that nanoparticle-pathogen complex formation was enhanced by small nanoparticle size rather than material or charge, and was prevented by 'stealth' modifications. Nanoparticles seem to preferentia…
Engineering of a Promoter Repressed by a Light-Regulated Transcription Factor in Escherichia coli
2021
Light-regulated gene expression systems allow controlling gene expression in space and time with high accuracy. Contrary to previous synthetic light sensors that incorporate two-component systems which require localization at the plasma membrane, soluble one-component repression systems provide several advantageous characteristics. Firstly, they are soluble and able to diffuse across the cytoplasm. Secondly, they are smaller and of lower complexity, enabling less taxing expression and optimization of fewer parts. Thirdly, repression through steric hindrance is a widespread regulation mechanism that does not require specific interaction with host factors, potentially enabling implementation…
Profiling of RNA modifications by multiplexed stable isotope labelling
2014
The combination of (15)N/(13)C stable isotope labelling (SIL) and LC-MS/MS revealed a total of 52 modifications in RNA from E. coli and yeast, including 10 previously undescribed modifications. Two modifications, N-ribosylnicotinamide and 2-methylthioadenosine, were newly detected in species hitherto thought not to contain these modifications.