Einfluß von 5-Azacytidin auf Reversion und UV-Sensibilität von Escherichia coli K12-Stämmen mit unterschiedlichen UVR-Genen / Influence of 5-Azacytidine on Reversion Rate and UV-Sensitivity of Escherichia coli K12 Strains with different UVR-Genes

1970 ◽  
Vol 25 (5) ◽  
pp. 537-542 ◽  
Author(s):  
R. Grunow ◽  
E. Geissler
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Phenotypic Expression ◽  
View Point ◽  
Reversion Rate ◽  
Bacterial Strains ◽  
Simultaneous Treatment ◽  
E Coli ◽  
Uv Sensitivity ◽  
Escherichia Coli K12

3 µg AC/ml cause an inhibition of cell division of E. coli K12 strains. This concentration is not mutagenic, because the reversion frequencies of the markers thr-, his- and arg- are not changed by AC treatment. However the reversion frequencies of thr- and arg- increased 1 to 4 orders of magnitude after UV irradiation, simultaneous treatment with AC and UV decreased these enlarged reversion rates at 1 exponent. The marker his- used in this experiments is not reverted by UV.The UV-sensitivity of bacterial strains with different uvr-genes is studied. The results are discussed from the view point that the influence of AC caused an inhibition of protein synthesis, whereby phenotypic expression of UV induced DNA damage is delayed and the time for repair of DNA is enlarged.

scholarly journals The Action of Bacteriophage Ω8 on Two Strains of Escherichia coli 08

Microbiology ◽  
2000 ◽  
Vol 81 (1) ◽  
pp. 131-144 ◽  
Author(s):  
Barbara Wallenfels ◽  
K. Jann
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Phage Particle ◽  
Cytoplasmic Membrane ◽  
Cellular Respiration ◽  
Bacterial Strains ◽  
Viral Dna ◽  
Killing Effect ◽  
E Coli ◽  
Phage Propagation

Bacteriophage Ω8 is propagated in Escherichia coli E56b (08: K27-:H-), a non-capsulated strain. Another non-capsulated strain, E. coli 2398 (08:K?-:H-), is killed by bacteriophage Ω8 without phage propagation. This strain was formerly believed to be E. coli 093:K?-:H-, cross-reacting with strain E56b. We have established chemical and serological identity of the 08-specific lipopolysaccharides of the two strains. The 08-specific lipopolysaccharides of both strains inhibited the infection of Escherichia coli E56b with bacteriophage Ω8 equally well. The adsorption rate constants of Ω8 were identical for the two strains of E. coli 08. Evidence was obtained with 32P-labelled bacteriophage Ω8 for penetration of viral DNA into both bacterial strains. In host strain E56b, phage particle synthesis occurred normally. In strain 2398 the viral DNA was not degraded but its expression was blocked. The killing effect of Ω8 on E. coli strain 2398 is supposed to be due to damage of the cytoplasmic membrane, which could not be reversed under the influence of viral information. This was indicated by a blockage of cellular respiration, β-galactoside transport and RNA as well as protein synthesis.

Enterohemorrhagic Escherichia coli Colony Check Assay for the Identification of Serogroups O26, O45, O103, O111, O121, O145, and O157 Colonies Isolated on Plating Media

2014 ◽  
Vol 77 (7) ◽  
pp. 1212-1218 ◽  
Author(s):  
BURTON BLAIS ◽  
MYLÈNE DESCHÊNES ◽  
GEORGE HUSZCZYNSKI ◽  
MARTINE GAUTHIER
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
High Throughput Screening ◽  
Enterohemorrhagic Escherichia Coli ◽  
Test Results ◽  
Bacterial Strains ◽  
Enrichment Broth ◽  
Substrate Solution ◽  
E Coli ◽  
Assay Performance

A simple immunoenzymatic enterohemorrhagic Escherichia coli (EHEC) colony check (ECC) assay was developed for the presumptive identification of priority EHEC colonies isolated on plating media from enrichment broth cultures of foods. With this approach, lipopolysaccharide extracted from a colony is spotted on the grid of a polymyxin-coated polyester cloth strip, and bound E. coli serogroup O26, O45, O103, O111, O121, O145, and O157 antigens are subsequently detected by sequential reactions with a pool of commercially available peroxidase-conjugated goat antibodies and tetramethylbenzidine substrate solution. Each strip can accommodate up to 15 colonies, and test results are available within 30 min. Assay performance was verified using colonies from a total of 73 target EHEC isolates covering the range of designated priority serogroups (all of which were reactive), 41 nontarget E. coli isolates including several nontarget Shiga toxin–producing E. coli serogroups (all unreactive), and 33 non–E. coli strains (all unreactive except two bacterial strains possessing O-antigenic structures in common with those of the priority EHEC). The ECC assay was reactive with target colonies grown on several types of selective and nonselective plating media designed for their cultivation. These results support the use of the ECC assay for high-throughput screening of colonies isolated on plating media for detecting priority EHEC strains in foods.

scholarly journals Utilization of Mn-Doped ZnSe/ZnS Core/Shell Quantum Dots for Rapid Detection of Escherichia coli O157:H7 and Methicillin-Resistant Staphylococcus aureus

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Thi-Diem Bui ◽  
Quang-Liem Nguyen ◽  
Thi-Bich Luong ◽  
Van Thuan Le ◽  
Van-Dat Doan
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Quantum Dots ◽  
Fluorescent Labeling ◽  
Core Shell ◽  
Bacterial Cells ◽  
Bacterial Strains ◽  
Methicillin Resistant ◽  
E Coli ◽  
Mn Doped

In this study, Mn-doped ZnSe/ZnS core/shell quantum dots (CSQDs) were synthesized in aqueous solution using polyethylene glycol as a surface stabilizer and successfully applied in the detection of Escherichia coli O157:H7 and methicillin-resistant Staphylococcus aureus (MRSA) for the first time. The CSQDs were conjugated with anti-E. coli antibody and anti-MRSA antibody via protein A supported by 1-ethyl-3-(-3-dimethylaminopropyl)carbodiimide hydrochloride for fluorescent labeling of the intact bacterial cells. The detection was performed for the bacterial strains cultivated in Luria-Bertani liquid medium. The obtained results indicate that E. coli O157:H7 and MRSA can be detected within 30 min at a high sensitivity of 101 CFU/mL. This labeling method based on the highly fluorescent CSQDs may have great potential for use in the food industry to check and prevent outbreaks of foodborne illness.

scholarly journals 617. Efficacy of Dimercaptosuccinic Acid (DMSA), a Zinc Chelator, in Combination with Imipenem Against Metallo-β-Lactamase Producing Escherichia coli in a Murine Peritonitis Model

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S287-S287
Author(s):  
Geoffrey Cheminet ◽  
Patrice Nordmann ◽  
Francoise Chau ◽  
Nicolas Kieffer ◽  
Katell Peoc’h ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Maximum Effect ◽  
Dependent Manner ◽  
Bacterial Strains ◽  
Concentration Dependent Manner ◽  
Bacterial Counts ◽  
E Coli ◽  
Zinc Chelator ◽  
Peritonitis Model

Abstract Background A strategy used by bacterial strains to resist β-lactam antibiotics is the expression of metallo-β-lactamases (MBL) requiring zinc for activity. The use of a zinc chelator may restore carbapenem activity against MBL-producing Enterobacteriaceae. DMSA is a heavy metal chelator approved in humans with a satisfactory safety record. Our objective was to evaluate the activity of DMSA in combination with carbapenems, in vitro and in a fatal murine peritonitis model, against MBL-producing Escherichia coli. Methods Isogenic derivatives of wild-type E. coli CFT073 producing the MBL NDM-1, VIM-2, IMP-1, and the serine carbapenemases OXA-48 and KPC-3 were constructed. Minimum inhibitory concentrations (MICs) of imipenem, meropenem, and ertapenem were determined against each strain alone or in combination with DMSA. Mice were infected with E. coli CFT073 or NDM-1 and treated intraperitoneally for 24 hours with imipenem 100 mg/kg every 4 hours, DMSA 200 mg/kg every 4 hours, or both. Mice survival rates and bacterial counts in peritoneal fluid (PF) and spleen were assessed at 24 hours. Results In vitro, DMSA in combination with each carbapenem permitted a significant decrease of the MICs against all MBL-producing strains, in a concentration-dependent manner. The maximum effect was found for the NDM-1 strain with a 6- to 8-fold MIC reduction, depending on the carbapenem used. NDM-1 strain became susceptible to carbapenems with concentrations of DMSA ≥6 mM. Increasing zinc concentrations above 1 mg/L (average human plasma concentration) did not alter this effect. No benefit of DMSA was observed against non-MBL strains. In vivo, when used alone, the DMSA regimen was not toxic in uninfected mice and ineffective against NDM-1-infected mice (100% mortality). Combination of imipenem and DMSA significantly reduced bacterial counts in PF and spleen as compared with imipenem alone (P < 0.001), and reduced mortality, although not significantly (11% vs. 37%, respectively, P = 0.12). No benefit of the combination was observed against CFT073. Conclusion DMSA is highly effective in vitro in reducing carbapenems MICs against MBL-producing E. coli and appears as a promising strategy in combination with carbapenems for the treatment of NDM-1-related infections. Disclosures All authors: No reported disclosures.

scholarly journals Laboratory-Dependent Bacterial Ecology: a Cautionary Tale

2006 ◽  
Vol 72 (4) ◽  
pp. 3032-3035 ◽  
Author(s):  
K. J. O'Keefe ◽  
N. M. Morales ◽  
H. Ernstberger ◽  
G. Benoit ◽  
P. E. Turner
Keyword(s):  
Escherichia Coli ◽  
Growth Medium ◽  
Equilibrium Composition ◽  
Cautionary Tale ◽  
Bacterial Strains ◽  
E Coli ◽  
Bacterial Ecology ◽  
Rule Out

ABSTRACT Although laboratory dependence is an acknowledged problem in microbiology, it is seldom intensively studied or discussed. We demonstrate that laboratory dependence is real and quantifiable even in the popular model Escherichia coli. Here laboratory effects alter the equilibrium composition of a simple community composed of two strains of E. coli. Our data rule out changes in the bacterial strains, chemical batches, and human handling but implicate differences in growth medium, especially the water component.

scholarly journals Induction of Human β-Defensin 2 by the Probiotic Escherichia coli Nissle 1917 Is Mediated through Flagellin

2007 ◽  
Vol 75 (5) ◽  
pp. 2399-2407 ◽  
Author(s):  
Miriam Schlee ◽  
Jan Wehkamp ◽  
Artur Altenhoefer ◽  
Tobias A. Oelschlaeger ◽  
Eduard F. Stange ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Culture Supernatant ◽  
Deletion Mutants ◽  
Strain Atcc ◽  
Bacterial Strains ◽  
Flagellin Gene ◽  
E Coli ◽  
Escherichia Coli Nissle 1917 ◽  
Stimulatory Factor ◽  
Escherichia Coli Nissle

ABSTRACT Human β-defensin 2 (hBD-2) is an inducible antimicrobial peptide synthesized by the epithelium to counteract bacterial adherence and invasion. Proinflammatory cytokines, as well as certain bacterial strains, have been identified as potent endogenous inducers. Recently, we have found that hBD-2 induction by probiotic Escherichia coli Nissle 1917 was mediated through NF-κB- and AP-1-dependent pathways. The aim of the present study was to identify the responsible bacterial factor. E. coli Nissle 1917 culture supernatant was found to be more potent than the pellet, indicating a soluble or shed factor. Chemical analysis demonstrated the factor to be heat resistant and proteinase digestible. Several E. coli Nissle 1917 deletion mutants were constructed and tested for their ability to induce hBD-2 expression in Caco-2 cells. Deletion mutants for flagellin specifically exhibited an impaired immunostimulatory capacity. Reinsertion of the flagellin gene restored the induction capacity to normal levels. Isolated flagellin from E. coli Nissle 1917 and from Salmonella enterica serovar Enteritidis induced hBD-2 mRNA significantly in contrast to the flagellin of the apathogenic E. coli strain ATCC 25922. H1 flagellin antiserum abrogated hBD-2 expression induced by flagellin as well as E. coli Nissle 1917 supernatant, confirming that flagellin is the major stimulatory factor of E. coli Nissle 1917.

scholarly journals Clonal Populations of ThermotolerantEnterobacteriaceae in Recreational Water and Their Potential Interference with Fecal Escherichia coli Counts

2001 ◽  
Vol 67 (10) ◽  
pp. 4934-4938 ◽  
Author(s):  
Sandra L. McLellan ◽  
Annette D. Daniels ◽  
Alissa K. Salmore
Keyword(s):  
Escherichia Coli ◽  
Water Samples ◽  
Environmental Protection Agency ◽  
16S Rrna Gene Sequencing ◽  
Fecal Coliforms ◽  
Rrna Gene ◽  
Bacterial Strains ◽  
Diverse Range ◽  
E Coli ◽  
Glucuronidase Activity

ABSTRACT Bacterial strains were isolated from beach water samples using the original Environmental Protection Agency method for Escherichia coli enumeration and analyzed by pulsed-field gel electrophoresis (PFGE). Identical PFGE patterns were found for numerous isolates from 4 of the 9 days sampled, suggesting environmental replication. 16S rRNA gene sequencing, API 20E biochemical testing, and the absence of β-glucuronidase activity revealed that these clonal isolates were Klebsiella, Citrobacter, and Enterobacter spp. In contrast, 82% of the nonclonal isolates from water samples were confirmed to be E. coli, and 16% were identified as other fecal coliforms. These nonclonal isolates produced a diverse range of PFGE patterns similar to those of isolates obtained directly from untreated sewage and gull droppings. β-Glucuronidase activity was critical in distinguishingE. coli from other fecal coliforms, particularly for the clonal isolates. These findings demonstrate that E. coli is a better indicator of fecal pollution than fecal coliforms, which may replicate in the environment and falsely elevate indicator organism levels.

Note: Effect of Some Spice Extracts on Bacterial Inhibition

2003 ◽  
Vol 9 (5) ◽  
pp. 353-358 ◽  
Author(s):  
O. Sagdic ◽  
A. G. Karahan ◽  
M. Ozcan ◽  
G. Ozkan
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Yersinia Enterocolitica ◽  
Inhibition Zone ◽  
Bacterial Strains ◽  
Inhibitory Effects ◽  
Antibacterial Effects ◽  
E Coli ◽  
Inhibition Zones ◽  
Mrs Broth

Eighteen extracts of spices commonly consumed worldwide and grown naturally in Turkey were tested against twenty three bacterial strains to compare their antibacterial effects with eleven antibiotics. Eight pathogens and fifteen lactobacilli isolated from chick intestine were used as the test microorganisms. Pathogens (six different Staphylococcus aureus strains, Escherichia coli ATCC 25922 and Yersinia enterocolitica ATCC 1501) were grown in Nutrient broth and lactobacilli in MRS broth. Hop extracts formed inhibition zones against S. aureus strains of upto 36 mm. Inhibitory effects of hop extracts against S. aureuswere generally higher than that of erythromycin as antibiotic. Helichrysum compactum extract produced an inhibition zone of 23mm to E. coli ATCC 25922 and 26mm to Y. enterocolitica ATCC 1501. Helichrysum compactum extract inhibited the growth of Y. enterocolitica ATCC 1501 more than other spice extracts. While inhibition zones of these extracts against lactobacilli were found smaller than on S. aureus strains, inhibition zones of the same extracts against lactobacilli were found similar to those of E. coli ATCC 25922 and Y. enterocolitica ATCC 1501.

scholarly journals Interactions between Penicillin-Binding Proteins (PBPs) and Two Novel Classes of PBP Inhibitors, Arylalkylidene Rhodanines and Arylalkylidene Iminothiazolidin-4-ones

2004 ◽  
Vol 48 (3) ◽  
pp. 961-969 ◽  
Author(s):  
Astrid Zervosen ◽  
Wei-Ping Lu ◽  
Zhouliang Chen ◽  
Ronald E. White ◽  
Thomas P. Demuth ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Cell Wall Synthesis ◽  
Bacterial Strains ◽  
Gram Negative ◽  
Penicillin Binding Proteins ◽  
E Coli ◽  
Peptidoglycan Biosynthesis ◽  
Vancomycin Resistant ◽  
Inhibitory Activities

ABSTRACT Several non-β-lactam compounds were active against various gram-positive and gram-negative bacterial strains. The MICs of arylalkylidene rhodanines and arylalkylidene iminothiazolidin-4-ones were lower than those of ampicillin and cefotaxime for methicillin-resistant Staphylococcus aureus MI339 and vancomycin-resistant Enterococcus faecium EF12. Several compounds were found to inhibit the cell wall synthesis of S. aureus and the last two steps of peptidoglycan biosynthesis catalyzed by ether-treated cells of Escherichia coli or cell wall membrane preparations of Bacillus megaterium. The effects of the arylalkylidene rhodanines and arylalkylidene iminothiazolidin-4-one derivatives on E. coli PBP 3 and PBP 5, Streptococcus pneumoniae PBP 2xS (PBP 2x from a penicillin-sensitive strain) and PBP 2xR (PBP 2x from a penicillin-resistant strain), low-affinity PBP 2a of S. aureus, and the Actinomadura sp. strain R39 and Streptomyces sp. strain R61 dd-peptidases were studied. Some of the compounds exhibited inhibitory activities in the 10 to 100 μM concentration range. The inhibition of PBP 2xS by several of them appeared to be noncompetitive. The dissociation constant for the best inhibitor (Ki = 10 μM) was not influenced by the presence of the substrate.

scholarly journals Enzymic synthesis of N-acetyl-l-phenylalanine in Escherichia coli K12

1971 ◽  
Vol 124 (5) ◽  
pp. 905-913 ◽  
Author(s):  
R. V. Krishna ◽  
P. R. Krishnaswamy ◽  
D. Rajagopal Rao
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Substrate Specificity ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
E Coli ◽  
Enzymic Synthesis ◽  
Escherichia Coli K12

1. Cell-free extracts of Escherichia coli K12 catalyse the synthesis of N-acetyl-l-phenylalanine from acetyl-CoA and l-phenylalanine. 2. The acetyl-CoA–l-phenylalanine α-N-acetyltransferase was purified 160-fold from cell-free extracts. 3. The enzyme has a pH optimum of 8 and catalyses the acetylation of l-phenylalanine. Other l-amino acids such as histidine and alanine are acetylated at slower rates. 4. A transacylase was also purified from E. coli extracts and its substrate specificity studied. 5. The properties of both these enzymes were compared with those of other known amino acid acetyltransferases and transacylases.

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