scholarly journals Characterization of BRPMBL, the Bleomycin Resistance Protein Associated with the Carbapenemase NDM

2017 ◽  
Vol 61 (3) ◽  
Author(s):  
Laurent Dortet ◽  
Delphine Girlich ◽  
Anne-Laure Virlouvet ◽  
Laurent Poirel ◽  
Patrice Nordmann ◽  
...  
Keyword(s):  
Specific Activity ◽  
Cloning And Expression ◽  
Cross Resistance ◽  
Dna Protection ◽  
Mobility Shift ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Resistance Protein

ABSTRACT The metallo-β-lactamase NDM-1 is among the most worrisome resistance determinants and is spreading worldwide among Gram-negative bacilli. A bleomycin resistance gene, ble MBL, downstream of the bla NDM-1 gene has been associated with resistance almost systematically. Here, we characterized the corresponding protein, BRPMBL, conferring resistance to bleomycin, an antitumoral glycopeptide molecule. We have determined whether the expression of the bla NDM-1-ble MBL operon is inducible in the presence of carbapenems and/or bleomycin-like molecules using quantitative reverse transcription-PCR (qRT-PCR), determination of imipenem and zeocin MICs, and carbapenemase-specific activity assays. We showed that the bla NDM-1-ble MBL operon is constitutively expressed. Using electrophoretic mobility shift and DNA protection assays performed with purified glutathione S-transferase (GST)-BRPMBL, we demonstrated that BRPMBL is able to bind and sequester bleomycin-like molecules, thus preventing bleomycin-dependent DNA degradation. In silico modeling confirmed that the mechanism of action required the dimerization of the BRPMBL protein in order to sequester bleomycin and prevent DNA damage. BRPMBL acts specifically on bleomycin-like molecules since cloning and expression of ble MBL in Staphyloccoccus aureus did not confer cross-resistance to any other antimicrobial glycopeptides such as vancomycin and teicoplanin.

scholarly journals Substrate Proteins Take Shape at an Improved Bacterial Translocon

2018 ◽  
Vol 201 (1) ◽  
Author(s):  
Donald Oliver
Keyword(s):  
Protein Transport ◽  
Protein Translocation ◽  
Membrane Vesicles ◽  
Transport Models ◽  
Content Type ◽  
Rate Limiting ◽  
Substrate Proteins

ABSTRACTCharacterization of Sec-dependent bacterial protein transport has often relied on anin vitroprotein translocation system comprised in part ofEscherichia coliinverted inner membrane vesicles or, more recently, purified SecYEG translocons reconstituted into liposomes using mostly a single substrate (proOmpA). A paper published in this issue (P. Bariya and L. Randall, J Bacteriol 201:e00493-18, 2019, https://doi.org/10.1128/JB.00493-18) finds that inclusion of SecA protein during SecYEG proteoliposome reconstitution dramatically improves the number of active translocons. This experimentally useful and intriguing result that may arise from SecA membrane integration properties is discussed here. Furthermore, determination of the rate-limiting transport step for nine different substrates implicates the mature region distal to the signal peptide in the observed rate constant differences, indicating that more nuanced transport models that respond to differences in protein sequence and structure are needed.

A new method for testing the force of clips for aneurysms or experimental spinal cord compression

1979 ◽  
Vol 51 (2) ◽  
pp. 229-233 ◽  
Author(s):  
Eugen J. Dolan ◽  
Charles H. Tator
Keyword(s):  
Spinal Cord ◽  
Early Detection ◽  
Spinal Cord Compression ◽  
Cord Compression ◽  
New Method ◽  
Content Type ◽  
Cosine Law ◽  
Fine Print

✓ A new method is described for the determination of force-distance curves for aneurysm clips. A dissecting microscope with a goniometer eyepiece was used to determine the angle between the clip blades as various forces were applied to open the clip. The cosine law was then used to calculate the force-distance curves. The method allows accurate characterization of different clips and is especially useful for the early detection of clip weakening.

scholarly journals Negative Regulation of Ectoine Uptake and Catabolism in Sinorhizobium meliloti: Characterization of the EhuR Gene

2016 ◽  
Vol 199 (1) ◽  
Author(s):  
Qinli Yu ◽  
Hanlin Cai ◽  
Yanfeng Zhang ◽  
Yongzhi He ◽  
Lincai Chen ◽  
...  
Keyword(s):  
Dna Binding ◽  
Sinorhizobium Meliloti ◽  
Binding Activity ◽  
Mobility Shift ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Dna Binding Activity ◽  
Dnase I Footprinting ◽  
Gntr Family

ABSTRACT Ectoine has osmoprotective effects on Sinorhizobium meliloti that differ from its effects in other bacteria. Ectoine does not accumulate in S. meliloti cells; instead, it is degraded. The products of the ehuABCD-eutABCDE operon were previously discovered to be responsible for the uptake and catabolism of ectoine in S. meliloti. However, the mechanism by which ectoine is involved in the regulation of the ehuABCD-eutABCDE operon remains unclear. The ehuR gene, which is upstream of and oriented in the same direction as the ehuABCD-eutABCDE operon, encodes a member of the MocR/GntR family of transcriptional regulators. Quantitative reverse transcription-PCR and promoter-lacZ reporter fusion experiments revealed that EhuR represses transcription of the ehuABCD-eutABCDE operon, but this repression is inhibited in the presence of ectoine. Electrophoretic mobility shift assays and DNase I footprinting assays revealed that EhuR bound specifically to the DNA regions overlapping the −35 region of the ehuA promoter and the +1 region of the ehuR promoter. Surface plasmon resonance assays further demonstrated direct interactions between EhuR and the two promoters, although EhuR was found to have higher affinity for the ehuA promoter than for the ehuR promoter. In vitro, DNA binding by EhuR could be directly inhibited by a degradation product of ectoine. Our work demonstrates that EhuR is an important negative transcriptional regulator involved in the regulation of ectoine uptake and catabolism and is likely regulated by one or more end products of ectoine catabolism. IMPORTANCE Sinorhizobium meliloti is an important soil bacterium that displays symbiotic interactions with legume hosts. Ectoine serves as a key osmoprotectant for S. meliloti. However, ectoine does not accumulate in the cells; rather, it is degraded. In this study, we characterized the transcriptional regulation of the operon responsible for ectoine uptake and catabolism in S. meliloti. We identified and characterized the transcription repressor EhuR, which is the first MocR/GntR family member found to be involved in the regulation of compatible solute uptake and catabolism. More importantly, we demonstrated for the first time that an ectoine catabolic end product could modulate EhuR DNA-binding activity. Therefore, this work provides new insights into the unique mechanism of ectoine-induced osmoprotection in S. meliloti.

scholarly journals A Statistical Approach for Determination of Disk Diffusion-Based Cutoff Values for Systematic Characterization of Wild-Type and Non-Wild-Type Bacterial Populations in Antimicrobial Susceptibility Testing

2015 ◽  
Vol 53 (6) ◽  
pp. 1812-1822 ◽  
Author(s):  
Giorgia Valsesia ◽  
Malgorzata Roos ◽  
Erik C. Böttger ◽  
Michael Hombach
Keyword(s):  
Resistance Mechanisms ◽  
Beta Lactamase ◽  
Wild Type ◽  
Beta Lactam ◽  
Bacterial Populations ◽  
Content Type ◽  
Extended Spectrum Beta Lactamase ◽  
E Coli

In this study, we introduce a new approach for determination of epidemiologic cutoffs (ECOFFs) and resistant-population cutoffs (RCOFFs) based on receiver operating characteristic (ROC) curves. As an example, the method was applied for determination of ECOFFs for seven different beta-lactam antibiotics and wild-type populations ofEscherichia coli,Klebsiella pneumoniae, andEnterobacter cloacae. In addition, RCOFFs were determined for bacterial populations with defined resistance mechanisms (“resistotypes”), i.e., extended-spectrum beta-lactamase (ESBL)-positiveE. coli, ESBL-positiveK. pneumoniae, and ESBL-positiveE. cloacae; AmpC cephalosporinase-positiveE. coliand AmpC-positiveK. pneumoniae; and broad-spectrum beta-lactamase (BSBL)-positiveE. coli. RCOFFs and ECOFFs are instrumental for a systematic characterization of associations between resistotypes and wild-type populations.

scholarly journals Characterization of the Highly Active Polyhydroxyalkanoate Synthase of Chromobacterium sp. Strain USM2

2011 ◽  
Vol 77 (9) ◽  
pp. 2926-2933 ◽  
Author(s):  
Kesaven Bhubalan ◽  
Jo-Ann Chuah ◽  
Fumi Shozui ◽  
Christopher J. Brigham ◽  
Seiichi Taguchi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Specific Activity ◽  
Weight Percent ◽  
Pha Synthase ◽  
Content Type ◽  
Highly Active ◽  
Key Enzyme ◽  
Polyhydroxyalkanoate Synthase

ABSTRACTThe synthesis of bacterial polyhydroxyalkanoates (PHA) is very much dependent on the expression and activity of a key enzyme, PHA synthase (PhaC). Many efforts are being pursued to enhance the activity and broaden the substrate specificity of PhaC. Here, we report the identification of a highly active wild-type PhaC belonging to the recently isolatedChromobacteriumsp. USM2 (PhaCCs). PhaCCsshowed the ability to utilize 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and 3-hydroxyhexanoate (3HHx) monomers in PHA biosynthesis. Anin vitroassay of recombinant PhaCCsexpressed inEscherichia colishowed that its polymerization of 3-hydroxybutyryl-coenzyme A activity was nearly 8-fold higher (2,462 ± 80 U/g) than that of the synthase from the model strainC. necator(307 ± 24 U/g). Specific activity using a Strep2-tagged, purified PhaCCswas 238 ± 98 U/mg, almost 5-fold higher than findings of previous studies using purified PhaC fromC. necator. Efficient poly(3-hydroxybutyrate) [P(3HB)] accumulation inEscherichia coliexpressing PhaCCsof up to 76 ± 2 weight percent was observed within 24 h of cultivation. To date, this is the highest activity reported for a purified PHA synthase. PhaCCsis a naturally occurring, highly active PHA synthase with superior polymerizing ability.

scholarly journals Phenotypic, Biochemical, and Genetic Analysis of KPC-41, a KPC-3 Variant Conferring Resistance to Ceftazidime-Avibactam and Exhibiting Reduced Carbapenemase Activity

2019 ◽  
Vol 63 (12) ◽  
Author(s):  
Linda Mueller ◽  
Amandine Masseron ◽  
Guy Prod’Hom ◽  
Tatiana Galperine ◽  
Gilbert Greub ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Klebsiella Pneumoniae ◽  
Genetic Analysis ◽  
Amino Acid Sequence ◽  
Cloning And Expression ◽  
Content Type ◽  
Amino Acid Insertion

ABSTRACT A novel KPC variant, KPC-41, was identified in a Klebsiella pneumoniae clinical isolate from Switzerland. This β-lactamase possessed a 3-amino-acid insertion (Pro-Asn-Lys) located between amino acids 269 and 270 compared to the KPC-3 amino acid sequence. Cloning and expression of the blaKPC-41 gene in Escherichia coli, followed by determination of MIC values and kinetic parameters, showed that KPC-41, compared to those of KPC-3, has an increased affinity to ceftazidime and a decreased sensitivity to avibactam, leading to resistance to ceftazidime-avibactam once produced in K. pneumoniae. Furthermore, KPC-41 exhibited a drastic decrease of its carbapenemase activity. This report highlights that a diversity of KPC variants conferring resistance to ceftazidime-avibactam already circulate in Europe.

scholarly journals Thermostable Chitosanase from Bacillus sp. Strain CK4: Cloning and Expression of the Gene and Characterization of the Enzyme

2000 ◽  
Vol 66 (9) ◽  
pp. 3727-3734 ◽  
Author(s):  
Ho-Geun Yoon ◽  
Hee-Yun Kim ◽  
Young-Hee Lim ◽  
Hye-Kyung Kim ◽  
Dong-Hoon Shin ◽  
...  
Keyword(s):  
Gene Sequence ◽  
Specific Activity ◽  
High Specific Activity ◽  
Industrial Applications ◽  
Cloning And Expression ◽  
Rrna Gene ◽  
Phenotypic Analysis ◽  
Reading Frame ◽  
The 16S Rrna Gene

ABSTRACT A thermostable chitosanase gene from the environmental isolateBacillus sp. strain CK4, which was identified on the basis of phylogenetic analysis of the 16S rRNA gene sequence and phenotypic analysis, was cloned, and its complete DNA sequence was determined. The thermostable chitosanase gene was composed of an 822-bp open reading frame which encodes a protein of 242 amino acids and a signal peptide corresponding to a 30-kDa enzyme. The deduced amino acid sequence of the chitosanase from Bacillus sp. strain CK4 exhibits 76.6, 15.3, and 14.2% similarities to those from Bacillus subtilis, Bacillus ehemensis, and Bacillus circulans, respectively. C-terminal homology analysis shows thatBacillus sp. strain CK4 belongs to cluster III withB. subtilis. The gene was similar in size to that of the mesophile B. subtilis but showed a higher preference for codons ending in G or C. The enzyme contains 2 additional cysteine residues at positions 49 and 211. The recombinant chitosanase has been purified to homogeneity by using only two steps with column chromatography. The half-life of the enzyme was 90 min at 80�C, which indicates its usefulness for industrial applications. The enzyme had a useful reactivity and a high specific activity for producing functional oligosaccharides as well, with trimers through hexamers as the major products.

scholarly journals Polymorphic Variation in Susceptibility and Metabolism of Triclosan-Resistant Mutants of Escherichia coli and Klebsiella pneumoniae Clinical Strains Obtained after Exposure to Biocides and Antibiotics

2015 ◽  
Vol 59 (6) ◽  
pp. 3413-3423 ◽  
Author(s):  
Tânia Curiao ◽  
Emmanuela Marchi ◽  
Carlo Viti ◽  
Marco R. Oggioni ◽  
Fernando Baquero ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Antimicrobial Susceptibility ◽  
Cross Resistance ◽  
Fitness Costs ◽  
Content Type ◽  
Relative Growth Rates ◽  
Global Regulators ◽  
E Coli ◽  
Reverse Transcription Pcr

ABSTRACTExposure to biocides may result in cross-resistance to other antimicrobials. Changes in biocide and antibiotic susceptibilities, metabolism, and fitness costs were studied here in biocide-selectedEscherichia coliandKlebsiella pneumoniaemutants.E. coliandK. pneumoniaemutants with various degrees of triclosan susceptibility were obtained after exposure to triclosan (TRI), benzalkonium chloride (BKC), chlorhexidine (CHX) or sodium hypochlorite (SHC), and ampicillin or ciprofloxacin. Alterations in antimicrobial susceptibility and metabolism in mutants were tested using Phenotype MicroArrays. The expression of AcrAB pump and global regulators (SoxR, MarA, and RamA) was measured by quantitative reverse transcription-PCR (qRT-PCR), and the central part of thefabIgene was sequenced. The fitness costs of resistance were assessed by a comparison of relative growth rates. Triclosan-resistant (TRIr) and triclosan-hypersusceptible (TRIhs) mutants ofE. coliandK. pneumoniaewere obtained after selection with biocides and/or antibiotics.E. coliTRIrmutants, including those with mutations in thefabIgene or in the expression ofacrB,acrF, andmarA, exhibited changes in susceptibility to TRI, CHX, and antibiotics. TRIrmutants for which the TRI MIC was high presented improved metabolism of carboxylic acids, amino acids, and carbohydrates. In TRIrmutants, resistance to one antimicrobial provoked hypersusceptibility to another one(s). TRIrmutants had fitness costs, particularlymarA-overexpressing (E. coli) orramA-overexpressing (K. pneumoniae) mutants. TRI, BKC, and CIP exposure frequently yielded TRIrmutants exhibiting alterations in AraC-like global regulators (MarA, SoxR, and RamA), AcrAB-TolC, and/or FabI, and influencing antimicrobial susceptibility, fitness, and metabolism. These various phenotypes suggest a trade-off of different selective processes shaping the evolution toward antibiotic/biocide resistance and influencing other adaptive traits.

scholarly journals Biochemical and Genetic Characterization of Carbapenem-Hydrolyzing β-Lactamase OXA-229 from Acinetobacter bereziniae

2012 ◽  
Vol 56 (7) ◽  
pp. 3923-3927 ◽  
Author(s):  
Rémy A. Bonnin ◽  
Alain A. Ocampo-Sosa ◽  
Laurent Poirel ◽  
Hélène Guet-Revillet ◽  
Patrice Nordmann
Keyword(s):  
Insertion Sequence ◽  
Carbapenem Resistance ◽  
Amino Acid Identity ◽  
Cloning And Expression ◽  
Skin Sample ◽  
Content Type ◽  
Promoter Sequences ◽  
Class D ◽  
Genetic Context

ABSTRACTAcinetobacter bereziniae(formerlyAcinetobactergenomospecies 10) isolate Nec was recovered from a skin sample of a patient hospitalized in Paris, France. It was resistant to penicillins, penicillin-inhibitor combinations, and carbapenems. Cloning and expression inEscherichia coliidentified the carbapenem-hydrolyzing class D β-lactamase OXA-229, which is weakly related to other oxacillinases (66% amino acid identity with the closest oxacillinase, OXA-58). It hydrolyzed penicillins, oxacillin, and imipenem but not expanded-spectrum cephalosporins. Sequencing of the genetic context of theblaOXA-229gene did not identify an insertion sequence but did identify mutations in the promoter sequences in comparison to the fully susceptibleA. bereziniaereference strain. The overexpression ofblaOXA-229inA. bereziniaeNec as a source of carbapenem resistance was identified by quantitative real-time PCR.

scholarly journals Salicylate Functions as an Efflux Pump Inducer and Promotes the Emergence of Fluoroquinolone-Resistant Campylobacter jejuni Mutants

2011 ◽  
Vol 77 (20) ◽  
pp. 7128-7133 ◽  
Author(s):  
Zhangqi Shen ◽  
Xiao-Ying Pu ◽  
Qijing Zhang
Keyword(s):  
Efflux Pump ◽  
Fold Increase ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Mobility Shift ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Resistant Mutants ◽  
Promoter Dna ◽  
Electrophoretic Mobility Shift Assays

ABSTRACTSalicylate, a nonsteroidal anti-inflammatory compound, has been shown to increase the resistance ofCampylobacterto antimicrobials. However, the molecular mechanism underlying salicylate-induced resistance has not yet been established. In this study, we determined how salicylate increases antibiotic resistance and evaluated its impact on the development of fluoroquinolone-resistantCampylobactermutants. Transcriptional fusion assays, real-time quantitative reverse transcription-PCR (RT-PCR), and immunoblotting assays consistently demonstrated the induction of the CmeABC multidrug efflux pump by salicylate. Electrophoretic mobility shift assays further showed that salicylate inhibits the binding of CmeR (a transcriptional repressor of the TetR family) to the promoter DNA ofcmeABC, suggesting that salicylate inhibits the function of CmeR. The presence of salicylate in the culture medium not only decreased the susceptibility ofCampylobacterto ciprofloxacin but also resulted in an approximately 70-fold increase in the observed frequency of emergence of fluoroquinolone-resistant mutants under selection with ciprofloxacin. Together, these results indicate that inCampylobacter, salicylate inhibits the binding of CmeR to the promoter DNA and induces expression ofcmeABC, resulting in decreased susceptibility to antibiotics and in increased emergence of fluoroquinolone-resistant mutants under selection pressure.

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