3,441 research outputs found
AgandCuloadedonTiO2/graphite as a catalyst for �Escherichia coli- contaminated water disinfection
No full textTiO2 film was synthesized by means of the chemical bath deposition (CBD) method from TiCl4
as a precursor and surfactant cetyl trimethyl ammonium bromide (CTAB) as a linking and assem-
bling agent of the titanium hydroxide network on a graphite substrate. Ag and Cu were loaded
on the TiO2 film by means of electrodeposition at various applied currents. Photoelectrochemical
testing on the composite of Ag–TiO2/G and Cu–TiO2/G was used to define the composite for
Escherichia coli-contaminated water disinfection. Disinfection efficiency and the rate of disinfection
of E. coli-contaminated water with Ag–TiO2/G as a catalyst was higher than that observed for
Cu–TiO2/G in all disinfection methods including photocatalysis (PC), electrocatalysis (EC), and
photoelectrocatalysis (PEC). The highest rate constant was achieved by the PEC method using
Ag–TiO2/G, k was 6.49 × 10−2
CFU mL−1
min−1
. Effective disinfection times of 24 h (EDT24)
and 48 h (EDT48) were achieved in all methods except the EC method using Cu–TiO2/G.
Keywords: Ag–TiO2/G, Cu–TiO2/G, Escherichia coli, disinfectio
Realizzazione di un sistema qualitativo in Real-Time PCR per l'identificazione di Escherichia Coli patogeni
No full textShiga toxin-producing E. coli (STEC-VTEC) are foodborne pathogens that have been associated with gastroenteric diseases in humans. Infections are often caused by ingestion of contaminated food. For this purpose, the report ‘Technical specifications for the monitoring and reporting of verotoxigenic Escherichia coli (VTEC o STEC) on animals and food (VTEC surveys on animals and food)’ was proposed by EFSA (European Food Safety Authority) in order to harmonize STEC research methods in EU Member States. Moreover, the reference method ISO 13136:2012 describes the molecular identification of Shiga toxin-producing E. coli through the detection of stx and eae virulence genes and serogroup assignment through the detection of the genes associated with O157, O111, O26, O103, O145 serogroups. The genes aggR and aaiC, distinctive for Enteroaggregative E. coli (EAEC) strains, should be also taken into account considering that the large outbreak occurred in Germany in 2011 (750 cases of HUS of which 44 deaths) was due to the consumption of sprouts contaminated by a O104 strain, which was found both STEC and EAEC (stx2, aggR and aaiC) positive.
The aim of this study was to develop a multiplex real-time PCR assay for the rapid detection of pathogenic E.coli strains in food, in particular an assay for the detection of stx1, stx2, and eae genes, which identifies STEC; other three assays specifically formulated for the identification of the six main pathogenic serogroups (O157, O111, O26, O103, O145, and O104), and , lastly, another assay for the detection of aggR and aaiC genes, specific for EAEC. Furthermore, the assays were compared with official methods used in USA (USDA-FSIS, FDA/BAM) for the identification of E.coli in foodstuffs.
The results obtained show that the assays for the sensitive, specific and rapid detection of STEC (stx-eae) and serogroups (O26-O103-O111-O145-O157-O104) were developed, in compliance with the reference method ISO 13136:2012. These assays were able to identify pathogenic E. coli in the main foodstuff implicated in epidemic outbreaks. Moreover, this work demonstrates that the performance of the assays is reliant on the enrichment process that remain a critical step in assay development. Since the contamination level of STEC in food is usually low, the selection of an appropriate medium is a key element of STEC detection protocol, to reduce the risk of false negative results. Therefore, alternative enrichment condition, like mBPWp + CV at 42°C, should be taken into consideration.
Furthermore, colony tests carried out with EAEC E.coli detection assay showed optimal results, with 100% of exclusivity and efficiency.
The comparison between molecular assays developed in this study and USDA-FSIS and FDA/BAM official methods showed equivalent results of performance and sensitivity, providing in some cases better results with our method
Size Dependence of Protein Diffusion in the Cytoplasm of Escherichia coli
No full textDiffusion in the bacterial cytoplasm is regarded as the primary method of intracellular protein movement and must play a major role in controlling the rates of cell processes. A number of recent studies have used green fluorescent protein (GFP) tagging and fluorescence microscopy to probe the movement and distribution of proteins in the bacterial cytoplasm. However, the dynamic behavior of indigenous proteins must be controlled by a complex mixture of specific interactions, combined with the basic physical constraints imposed by the viscosity and macromolecular crowding of the cytoplasm. These factors are difficult to unravel in studies with indigenous proteins. To what extent the addition of a GFP tag might affect the movement of a protein through the cytoplasm has also remained unknown. To resolve these problems, we have carried out a systematic study of the size dependence of protein diffusion coefficients in the Escherichia coli cytoplasm, using engineered GFP multimers (from 2 to 6 covalently linked GFP molecules). Diffusion coefficients were measured using confocal fluorescence recovery after photobleaching (FRAP). At least up to 110 kDa (four linked GFP molecules), the diffusion coefficient varies with size roughly as would be predicted from the Einstein-Stokes equation for a classical (Newtonian) fluid. Thus, protein diffusion coefficients are predictable over this range. GFP tagging of proteins has little impact on the diffusion coefficient over this size range and therefore need not significantly perturb protein movement. Two indigenous E. coli proteins were used to show that their specifi
Clustering and dynamics of cytochrome bd-I complexes in the Escherichia coli plasma membrane in vivo.
No full textThe cytochrome bd-I complex of Escherichia coli is a respiratory terminal oxidase and an integral component of the cytoplasmic membrane. As with other respiratory components, the organization and dynamics of this complex in living membranes is unknown. We set out to visualize the distribution and dynamics of this complex in vivo. By exchanging cydB for cydB-gfpgcn4 on the E. coli chromosome, we produced a strain (YTL01) that expresses functional GFP-tagged cytochrome bd-I terminal oxidase complexes under wild-type genetic control. We imaged live YTL01 cells using video-rate epifluorescence and total internal reflection fluorescence (TIRF) microscopy in combination with fluorescence recovery after photobleaching (FRAP) and saw mobile spots of GFP fluorescence in plasma membranes. Numbers of GFP molecules per spot were quantified by step-wise photobleaching giving a broad distribution with a mean of approximately 76, indicating that cytochrome bd-I is concentrated in mobile patches in the E. coli plasma membrane. We hypothesize that respiration occurs in mobile membrane patches which we call 'respirazones'
Photobiomodulation and Orthodontic Treatment with Clear Aligners: A Case Report of Severe Crowding and Agenesis
No full textThis paper aims to demonstrate the effectiveness of photobiomodulation in accelerating orthodontic treatment with clear aligners in correcting an orthodontic malocclusion characterized by severe crowding and agenesis in an adult subject. An adult male patient with Class I malocclusion, a mild Class III skeletal base and severe crowding was treated with 88 Invisalign® (Align Technology, Santa Clara, CA, USA) pairs of aligners replaced every 5 days in combination with an Orthopulse™ (Biolux Research, Vancouver, BC, Canada) photobiomodulation device for home use by the patient. The total orthodontic treatment time was 440 days. Orthopulse™ is a photobiomodulation device that generates continuous beams of near-infrared light (NIR—near-infrared) with a wavelength of 850 nm and a power of 42 mW/cm2 to produce an average energy density on the surface of the silicone impression of 9.3 J/cm2. The combined use of clear aligners and the Orthopulse™ device allowed the patient to replace the aligners according to an experimental 5-day protocol to speed up the orthodontic therapy and, thus, resolve the malocclusion in less time than the manufacturer’s standard
Cellular location and activity of Escherichia coli RecG proteins shed light on the function of its structurally unresolved C-terminus
No full textRecG is a DNA translocase encoded by most species of bacteria. The Escherichia coli protein targets branched DNA substrates and drives the unwinding and rewinding of DNA strands. Its ability to remodel replication forks and to genetically interact with PriA protein have led to the idea that it plays an important role in securing faithful genome duplication. Here we report that RecG co-localises with sites of DNA replication and identify conserved arginine and tryptophan residues near its C-terminus that are needed for this localisation. We establish that the extreme C-terminus, which is not resolved in the crystal structure, is vital for DNA unwinding but not for DNA binding. Substituting an alanine for a highly conserved tyrosine near the very end results in a substantial reduction in the ability to unwind replication fork and Holliday junction structures but has no effect on substrate affinity. Deleting or substituting the terminal alanine causes an even greater reduction in unwinding activity, which is somewhat surprising as this residue is not uniformly present in closely related RecG proteins. More significantly, the extreme C-terminal mutations have little effect on localisation. Mutations that do prevent localisation result in only a slight reduction in the capacity for DNA repair. © 2014 The Author(s)
Virulence Genes of Pathogenic Escherichia coli in Wild Red Foxes (Vulpes vulpes)
No full textSIMPLE SUMMARY: Escherichia coli is a commensal of the intestinal tract of humans and animals, but some pathotypes can cause severe infections. Enteropathogenic E. coli (EPEC), Shiga toxin-producing E. coli (STEC), and enterohemorrhagic E. coli (EHEC) are the pathotypes most frequently involved in enteric disorders observed in people and domestic animals. Wildlife may harbor and excrete these pathotypes too, therefore, they may be source of infections for humans and domestic animals. Vulpes vulpes seem to be involved in the epidemiology of pathogenic E. coli strains, and thus they could be a relevant threat mainly when they invade human settlements in rural and urban areas. ABSTRACT: Different pathotypes of Escherichia coli can cause severe diseases in animals and humans. Wildlife may contribute to the circulation of pathogenic pathotypes, including enteropathogenic E. coli (EPEC), Shiga toxin-producing E. coli (STEC), and enterohemorrhagic E. coli (EHEC). This study analyzed 109 DNA samples previously extracted from fecal specimens collected from red foxes (Vulpes vulpes) to detect E. coli virulence genes eaeA, hlyA, stx1, and stx2, that characterize the EPEC, STEC, and EHEC strains. Thirty-one (28.4%) samples were positive for at least one investigated virulence gene: eaeA gene was detected in 21 (19.2%) samples, hlyA in 10 (9.1%), stx1 in 6 (5.5%), and stx2 in 4 (3.6%). Nine DNA samples resulted positive for two or three virulence genes: five (4.6%) samples were positive for eaeA and hlyA genes, two (1.8%) for eaeA and stx1, one (0.9%) for hlyA and stx1, one (0.9%) for eaeA, hlyA and stx2. Red foxes seem to be involved in the epidemiology of these infections and their role could be relevant because they may be source of pathogenic E. coli for other wild animals, as well as domestic animals and humans
Photobiomodulation to Reduce Orthodontic Treatment Time in Adults: A Historical Prospective Study
No full textBackground: Orthodontic treatment in adult patients is hindered by several problems, such as little time for regular dental visits and financial costs. In recent years, photobiomodulation (PBM) has been shown to significantly reduce the duration of orthodontic treatment and significantly increase patient compliance. Objective: This study aimed to investigate the efficacy of PBM in shortening the orthodontic treatment duration in adult patients while ensuring optimal patient compliance. Methods: A total of 170 orthodontic patients with a Little’s irregularity index (LII) ≥ 3 mm treated with Invisalign clear aligners (Align Technology, Santa Clara, CA, USA) were included. The treatment group (PBM) (n = 90 patients) was trained in the use of the OrthopulseTM device (Biolux Research, Vancouver, Canada) according to an application protocol of 5 min per day. The control group (n = 80 patients) was treated with transparent Invisalign® without PBM applications. The LII was measured at a baseline and each aligner change until the end of the treatment when the LII was less than 1 mm. The crowding resolution rate (CRR), expressed in mm/week, and the total treatment time were measured. Results: The alignment rate of the PBM group was significantly higher than that of the control group (0.33 mm/week vs. 0.21 mm/week) with a reduction in the treatment time of 57.5 weeks in the PBM group compared with the control group. Conclusion: The PBM performed with the Orthopulse™ is shown to be an effective and noninvasive technique for accelerating teeth movements and can contribute in a relevant way to increase access to orthodontic treatment by the adult population as well as increase its compliance
Growth control of adherent-invasive Escherichia coli (AIEC) by the Predator Bacteria Bdellovibrio bacteriovorus: a new therapeutic approach for Crohn’s disease patients
No full textIn Crohn’s disease (CD) patients, intestinal dysbiosis with an overgrowth of Proteobacteria, mainly Escherichia coli, has been reported. A new pathotype of E. coli, the adherent-invasive Escherichia coli strain (AIEC), has been isolated from the mucosae of CD patients. AIEC strains play an important role in CD pathogenesis, increasing intestinal mucosa damage and inflammation. Several studies have been undertaken to find possible strategies/treatments aimed at AIEC strain reduction/elimination from CD patients’ intestinal mucosae. To date, a truly e↵ective strategy against AIEC overgrowth is not yet available, and as such, further investigations are warranted. Bdellovibrio bacteriovorus is a predator bacterium which lives by invading Gram-negative bacteria, and is usually present both in natural and human ecosystems. The aim of this study was to evaluate a novel possible strategy to treat CD patients’ mucosae when colonized by AIEC strains, based on the utilization of the Gram-negative predatory bacteria, B. bacteriovorus. The overall results indicate that B. bacteriovorus is able to interfere with important steps in the dynamics of pathogenicity of AIEC strains by its predatory activity. We indicate, for the first time, the possibility of counteracting AIEC strain overgrowth by exploiting what naturally occurs in microbial ecosystems (i.e., predation)
Localization of an accessory helicase at the replisome is critical in sustaining efficient genome duplication
No full text© The Author(s) 2010. Published by Oxford University PressGenome duplication requires accessory helicases to displace proteins ahead of advancing replication forks. Escherichia coli contains three helicases, Rep, UvrD and DinG, that might promote replication of protein-bound DNA. One of these helicases, Rep, also interacts with the replicative helicase DnaB. We demonstrate that Rep is the only putative accessory helicase whose absence results in an increased chromosome duplication time. We show also that the interaction between Rep and DnaB is required for Rep to maintain rapid genome duplication. Furthermore, this Rep–DnaB interaction is critical in minimizing the need for both recombinational processing of blocked replication forks and replisome reassembly, indicating that colocalization of Rep and DnaB minimizes stalling and subsequent inactivation of replication forks. These data indicate that E. coli contains only one helicase that acts as an accessory motor at the fork in wild-type cells, that such an activity is critical for the maintenance of rapid genome duplication and that colocalization with the replisome is crucial for this function. Given that the only other characterized accessory motor, Saccharomyces cerevisiae Rrm3p, associates physically with the replisome, our demonstration of the functional importance of such an association indicates that colocalization may be a conserved feature of accessory replicative motors.Biotechnology and Biological Sciences Research Council (BB/G005915/1 and BB/E0020690 to P.M.); MRC (G0800970 to R.G.L.); Leverhulme Trust (to C.J.R.). Funding for open access charge: BBSRC
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