scholarly journals Escherichia coli Resistance to Chlorine and Glutathione Synthesis in Response to Oxygenation and Starvation

1999 ◽  
Vol 65 (12) ◽  
pp. 5600-5603 ◽  
Author(s):  
Sébastien Saby ◽  
Pierre Leroy ◽  
Jean-Claude Block
Keyword(s):  
Escherichia Coli ◽  
Parent Strain ◽  
Reduced Glutathione ◽  
Glutathione Synthesis ◽  
E Coli ◽  
Oxygenation Rate

ABSTRACT Reduced glutathione (GSH) levels and resistance to chlorine were measured for two isogenic Escherichia coli strains stressed by oxygenation and/or starvation. The E. coli mutant deficient in GSH was not more sensitive to the oxidant than its parent strain when the bacteria were cultured with a low oxygenation rate. Starvation or oxygenation increased the resistance of the parent strain to chlorine, while the resistance of the deficient strain remained unchanged.

scholarly journals PBP5, PBP6 and DacD play different roles in intrinsic β-lactam resistance of Escherichia coli

Microbiology ◽  
2011 ◽  
Vol 157 (9) ◽  
pp. 2702-2707 ◽  
Author(s):  
Sujoy Kumar Sarkar ◽  
Mouparna Dutta ◽  
Chiranjit Chowdhury ◽  
Akash Kumar ◽  
Anindya S. Ghosh
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Parent Strain ◽  
Amino Acid Identity ◽  
Enzymic Activity ◽  
Exponential Phase ◽  
Wild Type ◽  
Acid Identity ◽  
Penicillin Binding Proteins ◽  
E Coli

Escherichia coli PBP5, PBP6 and DacD, encoded by dacA, dacC and dacD, respectively, share substantial amino acid identity and together constitute ~50 % of the total penicillin-binding proteins of E. coli. PBP5 helps maintain intrinsic β-lactam resistance within the cell. To test if PBP6 and DacD play simlar roles, we deleted dacC and dacD individually, and dacC in combination with dacA, from E. coli 2443 and compared β-lactam sensitivity of the mutants and the parent strain. β-Lactam resistance was complemented by wild-type, but not dd-carboxypeptidase-deficient PBP5, confirming that enzymic activity of PBP5 is essential for β-lactam resistance. Deletion of dacC and expression of PBP6 during exponential or stationary phase did not alter β-lactam resistance of a dacA mutant. Expression of DacD during mid-exponential phase partially restored β-lactam resistance of the dacA mutant. Therefore, PBP5 dd-carboxypeptidase activity is essential for intrinsic β-lactam resistance of E. coli and DacD can partially compensate for PBP5 in this capacity, whereas PBP6 cannot.

scholarly journals Efficacy of trimethoprim in murine experimental infection with a thymidine kinase-deficient mutant of Escherichia coli.

1997 ◽  
Vol 41 (5) ◽  
pp. 1042-1045 ◽  
Author(s):  
T Tokunaga ◽  
K Oka ◽  
A Takemoto ◽  
Y Ohtsubo ◽  
N Gotoh ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antimicrobial Activity ◽  
Thymidine Kinase ◽  
Mutant Strain ◽  
Experimental Infection ◽  
Therapeutic Efficacy ◽  
Parent Strain ◽  
E Coli

The antimicrobial activity of trimethoprim is antagonized by thymidine in in vitro susceptibility tests. The purpose of this investigation was to determine whether this antagonism also occurred during experimental infection in mice, which have high serum thymidine concentrations. We derived a mutant strain of Escherichia coli, TT-48, incapable of utilizing exogenous thymidine from parent strain E. coli KC-14 and then investigated the in vitro and in vivo antimicrobial activities of trimethoprim, sulfamethoxazole, cefdinir, and ofloxacin against these strains. E. coli TT-48 lacked the activity of thymidine kinase, which catalyzes the conversion of thymidine to thymidylate, but its growth curve remained close to that of the parent strain. The MICs of all of the antimicrobial agents tested, except cefdinir, for the mutant strain were slightly inferior to those for the parent strain. The bactericidal effect of trimethoprim against the parent strain was antagonized by thymidine at concentrations of more than 1 microg/ml, while that against the mutant strain was not affected by thymidine even at the highest concentration (10 microg/ml). The therapeutic efficacy of trimethoprim in experimental murine infections was significantly higher when the mutant rather than the parent strain was used, whereas the therapeutic efficacy of cefdinir or ofloxacin, whose antimicrobial action is independent of folic acid synthesis, was the same with both strains. Unexpectedly, sulfamethoxazole also had similar efficacy against both strains. Thus, high thymidine concentrations antagonized the antimicrobial activity of trimethoprim in vitro and in vivo.

scholarly journals Long Polar Fimbriae Contribute to Colonization by Escherichia coli O157:H7 In Vivo

2004 ◽  
Vol 72 (10) ◽  
pp. 6168-6171 ◽  
Author(s):  
Dianna M. Jordan ◽  
Nancy Cornick ◽  
Alfredo G. Torres ◽  
Evelyn A. Dean-Nystrom ◽  
James B. Kaper ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Parent Strain ◽  
Escherichia Coli O157 ◽  
Intestinal Colonization ◽  
E Coli ◽  
Gnotobiotic Piglets

ABSTRACT The contribution of long polar fimbriae to intestinal colonization by Escherichia coli O157:H7 was evaluated in sheep, conventional pigs, and gnotobiotic piglets. E. coli O157:H7 strains with lpfA1 and lpfA2 mutated were recovered in significantly lower numbers and caused fewer attachment and effacement lesions than the parent strain.

scholarly journals Effects of Ribosomal Protein S10 Flexible Loop Mutations on Tetracycline and Tigecycline Susceptibility of Escherichia coli

2021 ◽  
Vol 12 ◽  
Author(s):  
Norbert Izghirean ◽  
Claudia Waidacher ◽  
Clemens Kittinger ◽  
Miriam Chyba ◽  
Günther Koraimann ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Ribosomal Proteins ◽  
Parent Strain ◽  
Ribosomal Subunit ◽  
Tetracycline Resistance ◽  
E Coli ◽  
Growth Defects ◽  
Flexible Loop ◽  
Cold Sensitive ◽  
High Level

Tigecycline is a tetracycline derivative that is being used as an antibiotic of last resort. Both tigecycline and tetracycline bind to the small (30S) ribosomal subunit and inhibit translation. Target mutations leading to resistance to these antibiotics have been identified both in the 16S ribosomal RNA and in ribosomal proteins S3 and S10 (encoded by the rpsJ gene). Several different mutations in the S10 flexible loop tip residue valine 57 (V57) have been observed in tigecycline-resistant Escherichia coli isolates. However, the role of these mutations in E. coli has not yet been characterized in a defined genetic background. In this study, we chromosomally integrated 10 different rpsJ mutations into E. coli, resulting in different exchanges or a deletion of S10 V57, and investigated the effects of the mutations on growth and tigecycline/tetracycline resistance. While one exchange, V57K, decreased the minimal inhibitory concentration (MIC) (Etest) to tetracycline to 0.75 μg/ml (compared to 2 μg/ml in the parent strain) and hence resulted in hypersensitivity to tetracycline, most exchanges, including the ones reported previously in resistant isolates (V57L, V57D, and V57I) resulted in slightly increased MICs to tigecycline and tetracycline. The strongest increase was observed for the V57L mutant, with a MIC (Etest) to tigecycline of 0.5 μg/ml (compared to 0.125 μg/ml in the parent strain) and a MIC to tetracycline of 4.0 μg/ml. Nevertheless, none of these exchanges increased the MIC to the extent observed in previously described clinical tigecycline-resistant isolates. We conclude that, next to S10 mutations, additional mutations are necessary in order to reach high-level tigecycline resistance in E. coli. In addition, our data reveal that mutants carrying S10 V57 exchanges or deletion display growth defects and, in most cases, also thermosensitivity. The defects are particularly strong in the V57 deletion mutant, which is additionally cold-sensitive. We hypothesize that the S10 loop tip residue is critical for the correct functioning of S10. Both the S10 flexible loop and tigecycline are in contact with helix h31 of the 16S rRNA. We speculate that exchanges or deletion of V57 alter the positioning of h31, thereby influencing both tigecycline binding and S10 function.

scholarly journals The Gene Locus yijP Contributes to Escherichia coli K1 Invasion of Brain Microvascular Endothelial Cells

1999 ◽  
Vol 67 (9) ◽  
pp. 4751-4756 ◽  
Author(s):  
Ying Wang ◽  
Sheng-He Huang ◽  
Carol A. Wass ◽  
Monique F. Stins ◽  
Kwang Sik Kim
Keyword(s):  
Escherichia Coli ◽  
Endothelial Cells ◽  
Blood Brain Barrier ◽  
Parent Strain ◽  
Gene Locus ◽  
Brain Barrier ◽  
Microvascular Endothelial Cells ◽  
Brain Microvascular Endothelial Cells ◽  
E Coli ◽  
Blood Brain

ABSTRACT Most cases of Escherichia coli meningitis develop as a result of hematogenous spread, but it is not clear how circulatingE. coli crosses the blood-brain barrier. A TnphoA mutant of E. coli K1 RS218 was shown to be significantly less invasive than its parent strain in bovine and human brain microvascular endothelial cells (BMEC), which constitute the blood-brain barrier. More importantly, traversal of the blood-brain barrier was significantly less with this mutant than with the parent strain in newborn rats with experimental hematogenous meningitis. A DNA segment containing the TnphoA insertion site was cloned from RS218, and the cloned DNA complemented the TnphoAmutant in invasion of BMEC. Nucleotide sequence revealed a near identity to that of a hypothetical yijP gene (also calledf577) in the E. coli K-12 genome. Sequence analysis indicated that the E. coli K1 yijPgene likely encodes a 66.6-kDa membrane protein. Deletion and complementation experiments indicated that the yijP gene was involved in E. coli K1 invasion of BMEC, i.e., the invasive ability of E. coli K1 was significantly reduced after yijP was deleted and was restored by complementation with a plasmid containing the yijP open reading frame. This is the first demonstration that the yijP gene locus plays a role in the pathogenesis of E. coli K1 meningitis.

scholarly journals Regulation of Cell Division, Biofilm Formation, and Virulence by FlhC in Escherichia coli O157:H7 Grown on Meat

2011 ◽  
Vol 77 (11) ◽  
pp. 3653-3662 ◽  
Author(s):  
Preeti Sule ◽  
Shelley M. Horne ◽  
Catherine M. Logue ◽  
Birgit M. Prüß
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Real Time ◽  
Real Time Pcr ◽  
Biofilm Formation ◽  
Parent Strain ◽  
Cellular Functions ◽  
Content Type ◽  
E Coli ◽  
K 12

ABSTRACTTo understand the continuous problems thatEscherichia coliO157:H7 causes as food pathogen, this study assessed global gene regulation in bacteria growing on meat. Since FlhD/FlhC ofE. coliK-12 laboratory strains was previously established as a major control point in transducing signals from the environment to several cellular processes, this study compared the expression pattern of anE. coliO157:H7 parent strain to that of its isogenicflhCmutant. This was done with bacteria that had been grown on meat. Microarray experiments revealed 287 putative targets of FlhC. Real-time PCR was performed as an alternative estimate of transcription and confirmed microarray data for 13 out of 15 genes tested (87%). The confirmed genes are representative of cellular functions, such as central metabolism, cell division, biofilm formation, and pathogenicity. An additional 13 genes from the same cellular functions that had not been hypothesized as being regulated by FlhC by the microarray experiment were tested with real-time PCR and also exhibited higher expression levels in theflhCmutant than in the parent strain. Physiological experiments were performed and confirmed that FlhC reduced the cell division rate, the amount of biofilm biomass, and pathogenicity in a chicken embryo lethality model. Altogether, this study provides valuable insight into the complex regulatory network of the pathogen that enables its survival under various environmental conditions. This information may be used to develop strategies that could be used to reduce the number of cells or pathogenicity ofE. coliO157:H7 on meat by interfering with the signal transduction pathways.

scholarly journals Shiga Toxin and Shiga Toxin-Encoding Phage Do Not Facilitate Escherichia coli O157:H7 Colonization in Sheep

2006 ◽  
Vol 73 (1) ◽  
pp. 344-346 ◽  
Author(s):  
Nancy A. Cornick ◽  
Amy F. Helgerson ◽  
Vijay Sharma
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Parent Strain ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Isogenic Strains

ABSTRACT Isogenic strains of Escherichia coli O157:H7, missing either stx 2 or the entire Stx2-encoding phage, were compared with the parent strain for their abilities to colonize sheep. The absence of the phage or of the Shiga toxin did not significantly impact the magnitude or duration of shedding of E. coli O157:H7.

Identification of a trans-dominant mutation affecting proline dehydrogenase in Escherichia coli

1985 ◽  
Vol 31 (11) ◽  
pp. 988-993 ◽  
Author(s):  
Charles E. Deutch ◽  
John M. O'Brien Jr. ◽  
Michael S. VanNieuwenhze
Keyword(s):  
Escherichia Coli ◽  
Enzyme Activity ◽  
Parent Strain ◽  
Specific Activity ◽  
Deficient Mutant ◽  
Proline Dehydrogenase ◽  
Dominant Mutation ◽  
E Coli ◽  
F Factor ◽  
K 12

L-Proline dehydrogenase catalyzes the oxidation of L-proline to Δ1-pyrroline-5-carboxylate, a reaction that is an important step in the utilization of proline as a carbon or nitrogen source by bacteria. A mutant of Escherichia coli K-12 lacking L-leucyl-tRNA:protein transferase had been found previously to contain about five times as much proline dehydrogenase activity as its parent strain. This difference has now been shown to be due to the presence in the parent strain of a previously unrecognized mutation. This mutation, which has been designated put-4977, specifically affects proline dehydrogenase rather than proline uptake. Although proline dehydrogenase remains inducible by L-proline in strains carrying the mutation, there is a premature cessation of differential synthesis during induction that results in a lower specific activity. The mutation shows about 50% P1-mediated cotransduction with pyrC and is therefore located at about 22 min on the E. coli chromosome. Merodiploids containing a normal F′ factor still exhibit decreased enzyme activity, indicating that the put-4977 mutation is trans-dominant. The mutation cannot be detected in present stocks of the transferase-deficient mutant, suggesting that this mutant is a revertant for put-4977.

Isolation and partial characterization of an Escherichia coli mutant resistant to colicin A

1975 ◽  
Vol 21 (10) ◽  
pp. 1595-1601 ◽  
Author(s):  
Marc Lavoie ◽  
Leo G. Mathieu
Keyword(s):  
Escherichia Coli ◽  
Methylene Blue ◽  
Parent Strain ◽  
General Pattern ◽  
Sodium Dodecyl ◽  
Triphenyltetrazolium Chloride ◽  
E Coli ◽  
Receptor Sites ◽  
Acridine Dyes

An Escherichia coli K12 mutant resistant to colicin A-CA31 apparently through loss of its receptor sites has been isolated and partially characterized. Resistance to colicin A was accompanied with a decreased sensitivity to colicins L-398 and E2-CA42, and to acridine dyes. The mutant strain displayed the same general pattern of tolerance or sensitivity as the parent strain towards eight antibiotics, colicins C, D, E1, E3, F2, F3, G, I, K, and N; phages T1, T2, T5, T6, T7, F2, λ vir, P1kc, [Formula: see text] 80, and BF23; and to methylene blue, triphenyltetrazolium chloride, ethylene-diaminetetraacetate (EDTA), deoxycholate, and sodium dodecyl sulfate. Conjugation and transduction experiments showed that a locus controlling resistance to colicin A-CA31 mapped at 21 min on the genetic map of this E. coli K12 strain.

scholarly journals Colonization of Gnotobiotic Piglets by a luxS Mutant Strain of Escherichia coli O157:H7

2005 ◽  
Vol 73 (2) ◽  
pp. 1214-1216 ◽  
Author(s):  
Dianna M. Jordan ◽  
Vanessa Sperandio ◽  
James B. Kaper ◽  
Evelyn A. Dean-Nystrom ◽  
Harley W. Moon
Keyword(s):  
Escherichia Coli ◽  
Mutant Strain ◽  
Parent Strain ◽  
Clinical Symptoms ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Luxs Mutant ◽  
Mutant Derivative ◽  
Gnotobiotic Piglets

ABSTRACT Gnotobiotic piglets inoculated with Escherichia coli O157:H7, its luxS mutant derivative, or nonpathogenic E. coli were evaluated for attaching and effacing lesions. Although no differences in clinical symptoms were seen between pigs inoculated with the parent and those inoculated with the luxS mutant, the luxS mutant-inoculated pigs had a lower frequency of attaching and effacing lesions in the spiral colon than parent strain-inoculated pigs.

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