3,092 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
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'
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)
Guia do arquivo pessoal de Helios Seelinger
No full textGuia descritivo do Arquivo pessoal de Helios Aristides Seelinger (Rio de Janeiro, RJ 1878 - Rio de Janeiro, RJ 1965), realizado no âmbito da pesquisa de doutorado de João Victor Rossetti Brancato no Programa de Pós-Graduação em História da Universidade Estadual de Campinas (UNICAMP) entre 2019 e 2025, sob orientação do Prof. Jorge Coli e financiamento da pesquisa pela Fundação de Amparo à Pesquisa do Estado de São Paulo (Processo nº 19/08063-8). A realização do Guia contou com o apoio de Heloisa Maria Seelinger Pereira da Silva, guardiã do arquivo do artista.
Em 2020, parte dos documentos do arquivo foram doados ao Centro de Documentação e Memória da Pinacoteca do Estado de São Paulo, constituindo o Fundo Helios Seelinger (BR SPPSP HS), composto por 339 itens identificados pelo intervalo de notação HS.00001 a HS.00339 e disponível online em: http://biblioteca.pinacoteca.org.br:9090/site/php/index.php. No Guia a seguir, produzido entre 2019 e 2020 e atualizado em 2025, são descritos sumariamente todos os itens localizados no arquivo antes da doação
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
Characterization of Escherichia coli strains carrying different rpos alleles.
No full textA bactéria Escherichia coli é encontrada em diversos habitats e deve estar preparada para sobreviver e crescer em condições desfavoráveis. A adaptação da bactéria a diferentes condições obriga-a a controlar a expressão de genes de forma eficiente. Uma das formas primárias de controle de expressão gênica é a competição entre os diversos fatores sigma pela ligação ao cerne da RNA polimerase. <font face=\"Symbol\">d70 é o fator sigma mais abundante e participa da transcrição da maioria dos genes de E. coli, enquanto que <font face=\"Symbol\">dS é o segundo em importância e reconhece promotores de genes relacionados à resposta geral ao estresse. O gene rpoS, que codifica para <font face=\"Symbol\">dS é altamente polimórfico, e adquiri mutações frequentemente. A mutação pontual C<font face=\"Symbol\">®T na posição 97 da ORF de rpoS, resulta em um códon de parada TAG (âmbar). Um Shine-Dalgarno alternativo e um códon de início de tradução na posição 157 dá início a uma proteína RpoS truncada, que é parcialmente funcional. Uma das situações de estresse na qual <font face=\"Symbol\">dS é ativado corresponde à privação de fosfato inorgânico. Porém, na limitação deste nutriente ocorre também a ativação do regulon PHO, cujos genes são predominantemente transcritos por <font face=\"Symbol\">d70. Neste trabalho, o efeito da versão truncada de RpoS sobre a expressão de genes dependentes de <font face=\"Symbol\">d70 (lacZ, phoA e pstS) e de genes dependentes de <font face=\"Symbol\">dS (osmY e proU) foi testado. Foram também realizados ensaios de estresse oxidativo, osmótico e pelo frio. O perfil de atividade parcial descrito para RpoSam pôde ser observado em alguns casos, porém em outros o comportamento deste alelo se assemelhou ao do mutante rpoS nulo. Paralelamente, foi testada também uma cepa de E. coli que carrega a mutação âmbar em rpoS, mas esta é suprimida, resultando na expressão de uma proteína RpoS normal. A proteína RpoS truncada não pôde ser visualizada em immunoblots, provavelmente porque esta é traduzida de forma pouco eficiente a partir do Shine-Dalgarno alternativo. Com o objetivo de incrementar a detecção de RpoS em ensaios de imuno-detecção, foi inserida por recombinação alélica uma etiqueta SPA altamente imunogênica na porção C-terminal da proteína.Escherichia coli can be found in many different habitats and has to be prepared to survive and grow under unfavorable conditions. Bacteria adaptation to different growth conditions requires an efficient control of gene expression. One of the primary forms of gene expression control is the competition between different sigma factors for the binding to the core RNA polymerase. <font face=\"Symbol\">d70 is the most abundant sigma factor and participates in the transcription of most E. coli genes. <font face=\"Symbol\">dS is the second one in importance and recognizes promoters of genes related to the general stress response. The rpoS gene, which encodes <font face=\"Symbol\">dS, is highly polymorphic and acquires mutations very often. The transition C<font face=\"Symbol\">®T at position 97 in the rpoS ORF results in a stop codon TAG (amber). Due to the presence of an alternative Shine-Dalgarno and a translation initiation codon at position 157 a truncated RpoS protein that is partially functional is translated. One of the stress situations that <font face=\"Symbol\">dS is activated is the starvation for inorganic phosphate. Phosphate limitation also triggers the activation of the PHO regulon, whose genes are predominantly transcribed by <font face=\"Symbol\">d70. In the present study, the effect of the truncated version of RpoS on the expression of <font face=\"Symbol\">d70 dependent genes (lacZ, phoA e pstS) and <font face=\"Symbol\">dS dependent genes (osmY e proU) was tested. Bacteria were also assayed for sensitivity to oxidative, osmotic and cold stress. The profile of partial activity described for the truncated RpoS could be observed in some cases, while in others the behavior of this allele resembled the rpoS null mutant. In parallel, an E. coli strain which suppresses the amber mutation in RpoS, resulting in the expression of a normal protein was also tested. A band correponding to the truncated RpoS could not be detected in immunoblots probably due to inefficient translation from the alternative Shine-Dalgarno. To improve the detection of RpoS, a highly immunogenic SPA tag was inserted in the C-terminal region of the protein
Recurrent clinical mastitis caused by Escherichia coli in dairy cows
No full textIn this study, the occurrence of persistent intramammary infections caused by Escherichia coli with recurrent episodes of clinical mastitis caused by E. coli are described for a cohort of 300 Dutch dairy herds. Calculations on the recurrent episodes were based on data collected by dairy farmers. The genotype of the E. coli strains was determined by means of a polymerase chain reaction using enterobacterial repetitive intergenic consensus (ERIC) primers, resulting in a DNA fingerprint. Quarters in which the same E. coli genotype was found were considered to be persistently infected. In 4.77% of all episodes of clinical mastitis caused by E. coli, persistent intramammary infections caused by the same E. coli genotype were found. Based on the occurrence of the same genotypes, we concluded that, in 2.98% of all episodes, transmission of E. coli strains among quarters within one cow might have occurred. In 13.04% of all episodes of clinical mastitis caused by E. coli in the study, different E. coli genotypes were isolated from recurrent episodes of clinical mastitis within the same cow, indicating that these cows were highly susceptible to recurrent intramammary infections caused by E. coli.LR: 20031114; PUBM: Print; JID: 2985126R; ppublishSource type: Electronic(1
Encapsulation of E. coli phage ZCEC5 in chitosan-alginate beads as a delivery system in phage therapy
No full text© 2019, The Author(s). Bacteriophages can be used successfully to treat pathogenic bacteria in the food chain including zoonotic pathogens that colonize the intestines of farm animals. However, harsh gastric conditions of low pH and digestive enzyme activities affect phage viability, and accordingly reduce their effectiveness. We report the development of a natural protective barrier suitable for oral administration to farm animals that confers acid stability before functional release of bead-encapsulated phages. Escherichia coli bacteriophage ZSEC5 is rendered inactive at pH 2.0 but encapsulation in chitosan–alginate bead with a honey and gelatin matrix limited titer reductions to 1log10PFUmL−1. The encapsulated phage titers were stable upon storage in water but achieved near complete release over 4–5h in a simulated intestinal solution (0.1% bile salt, 0.4% pancreatin, 50mM KH2PO4 pH 7.5) at 37°C. Exposure of E. coli O157:H7 to the bead-encapsulated phage preparations produced a delayed response, reaching a maximal reductions of 4.2 to 4.8log10CFUmL−1 after 10h at 37°C under simulated intestinal conditions compared to a maximal reduction of 5.1log10CFUmL−1 at 3h for free phage applied at MOI = 1. Bead-encapsulation is a promising reliable and cost-effective method for the functional delivery of bacteriophage targeting intestinal bacteria of farm animals
Exposure of embryonating eggs to Enterococcus faecalis and Escherichia coli potentiates E. coli pathogenicity and increases mortality of neonatal chickens
No full textEnterococci and Escherichia coli are opportunistic pathogens of poultry and are associated with embryo and neonatal chick mortality. We have recently demonstrated that 56% of dead broiler chicken embryos in commercial hatcheries in western Canada were due to the coinfection of Enterococcus species and E. coli. The objective of this study was to investigate the host-pathogen interactions of Enterococcus faecalis and E. coli in developing chicken embryos. Embryonating eggs at 12 d of incubation were dipped in a solution of E. faecalis and/or E. coli for 30 s to expose the eggshell to study the migration and colonization of E. faecalis and E. coli in the internal organs of chicken embryos and subsequent neonatal chicken mortality following hatch. A multidrug-resistant E. faecalis isolate from a dead chicken embryo and an E. faecalis isolate from a case of yolk sac infection were able to colonize the internal organs of chicken embryos rapidly compared to an E. faecalis isolate from a healthy chicken without affecting viability or hatchability of embryos. Although E. faecalis colonized internal organs of chicken embryos, no evidence of inflammation of these organs nor the expression of virulence genes of E. faecalis was observed. Although E. faecalis and E. coli alone did not affect the viability of embryos, a significantly high neonatal chicken mortality (27%) was observed following exposure of embryos to both E. faecalis and E. coli. Upregulation of IL-1 and CXCR4 was evident 48 h before peak mortality of neonatal chickens; this could suggest a possible link of cytokine dysregulation to increased mortality in coinfected neonatal chickens. However, further studies are warranted to investigate this issue vis-à-vis coinfection with E. faecalis and E. coli in chicken embryos and neonatal chickens.Alberta Agriculture and Forestry, Alberta, CanadaNatural Sciences and Engineering Research Council of Canad
Characterization of traditional kefir on physicalchemical composition, sensorial characteristic and anti-Escherichia coli activity
No full textKefir é um alimento fermentado resultante da dupla fermentação do leite pelos grãos de kefir, sendo estes grãos uma associação simbiótica de leveduras, bactérias ácido-láticas e bactérias ácido-acéticas. Do kefir pode-se obter o kefir leban e o soro de kefir, ambos resultantes da filtração do kefir em tecido de algodão esterilizado, por 24 horas, a 25ºC ± 2ºC. Este estudo tem por objetivos caracterizar e avaliar o comportamento de diferentes amostras de grãos de kefir tradicional e de derivados (kefir, kefir leban e soro de kefir) quanto às características físico-químicas, sensoriais, intenção de compra e atividade anti-Escherichia coli, quando inoculados em diferentes concentrações, padronizando-se o tipo de leite, o tempo e a temperatura de incubação, a maturação e a filtração. Foram desenvolvidas análises fisicoquímicas, a avaliação sensorial através do teste de aceitabilidade e preferência e a determinação de atividade anti-Escherichia coli. Os resultados demonstraram que a técnica de manipulação e padronização das amostras foi eficaz na obtenção de produtos com características idênticas, visto a reprodutibilidade dos resultados. Também indicam que o volume de leite utilizado na incubação influencia significativamente nas características do produto final. O kefir leban obtido do experimento apresentou consistência cremosa, semelhante ao queijo quark, aroma característico de laticínio fermentado, cor amarela esbranquiçada, sabor ácido e boa espalhabilidade. Manteve os teores de cálcio contidos no leite após o processamento, concentrou as proteínas e gorduras, além de não conter lactose. Apresentou boa aceitabilidade e 58% de intenção de compra, quando utilizado na elaboração de formulações alimentares tipo antepasto. O kefir e o soro de kefir apresentaram Intensidade de Atividade de Inibição Bacteriana/bacteriostasia e Intensidade de Atividade de Inativação Bacteriana/ bactericidia máximas frente ao inóculo bacteriano Escherichia coli (ATCC 11229), testado em concentrações <=108 UFC/mL.Kefir is a fermented food resulting from the double fermentation of milk by kefir grains, these grains are a symbiotic association of yeasts, acid-lactic and acetic-acid bacteria. From kefir can be obtained kefir leban and kefir whey, both from the filtration of kefir in sterile cotton cloth, during 24 hours at 25°C ± 2ºC. This study aims to characterize and evaluate the behavior of different samples of traditional kefir grains and products derived (kefir, kefir leban and kefir whey) on the physicochemical composition, sensorial characteristic, intent to buy and anti-Escherichia coli activity, when inoculated in different concentrations, standardized the type of milk, the time and temperature of incubation, the maturation and filtration processes. Were developed physical and chemical analysis, the sensory evaluation using the tests of acceptability and preference and determination of anti-Escherichia coli activity. The results showed that the technique of handling and standardizing of the samples was effective in providing products with similar characteristics as the reproductibility of results. It is also indicate that the volume of milk used in the incubation influence significantly the characteristics of the final product. The kefir leban obtained in the experiment showed creamy consistency, similar to quark cheese, characteristic aroma of fermented dairy, whitish yellow color, acid flavor and good spread. He maintained the calcium contained in milk after processing,he concentrated protein, and don't contain any lactose. The product showed good acceptability and 58% of purchase intention, when used in the preparation of food formulations such hors d'oeuvre. The kefir and the kefir whey showed maximal intensity of bacterial inhibition activity/bacteriostasys, and intensity of bacterial inactivation activity/bactericidie in front of inoculum of Escherichia coli (ATCC 11229), tested at concentrations <=108CFU/mL
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