scholarly journals Activity Spectrum of Colicins Produced by Shigella sonnei and Genetic Mechanism of Colicin Resistance in Conspecific S. sonnei Strains and Escherichia coli

2014 ◽  
Vol 59 (1) ◽  
pp. 152-158 ◽  
Author(s):  
Fatema Calcuttawala ◽  
Chellaram Hariharan ◽  
Gururaja P. Pazhani ◽  
Santanu Ghosh ◽  
Thandavarayan Ramamurthy
Keyword(s):  
Escherichia Coli ◽  
Shigella Sonnei ◽  
Genetic Mechanism ◽  
Vitamin B ◽  
Content Type ◽  
E Coli ◽  
Fluctuation Test ◽  
Uptake Assay ◽  
Activity Spectrum

ABSTRACTColicin-mediated killing is an example of allelopathy, which has been found among several bacteria. Screening of 42 strains ofShigella sonneiisolated from diarrheal patients revealed that 39 (93%)S. sonneistrains were positive for colicin production againstEscherichia coliDH5α. In the PCR-based detection of the colicin types, 36 (92.3%) were identified as E3, 2 (5.1%) as E3 and E8, and 1 (2.6%) as E3 and E2. RepresentativeS. sonneistrains producing heterologous colicins exhibited antagonism against diarrheagenicEscherichia coli(DEC) groups. Although it is known that mutation in the colicin receptor renders the host resistant to colicin, there is a dearth of information on the genetic characterization of such mutants. In the fluctuation test, colicin-resistantE. colimutants were found to occur spontaneously at the rates of 2.51 × 10−8and 5.52 × 10−8per generation when exposed to colicins E3 and E8 and colicins E3 and E2, respectively. Genotypic characterization of colicin-resistantE. coli(ECCr) andS. sonnei(SSCr) strains displayed mutations in thebtuBgene, which encodes the receptor for vitamin B12uptake. This gene was interrupted by various insertion sequences, such as IS1, IS2, and IS911. Complementation of ECCrand SSCrwith plasmid-bornebtuB(pbtuB) accomplished restoration of the colicin-susceptible phenotype. The vitamin B12uptake assay gave an insight into the physiological relevance of thebtuBmutation. Our studies provide insights into the latent influence ofS. sonneicolicins in governing the existence of some of the shigellae and all of the DEC and the genetic mechanism underlying the emergence of resistance.

scholarly journals Identification and Characterization of Genes Required for 5-Hydroxyuridine Synthesis in Bacillus subtilis and Escherichia coli tRNA

2019 ◽  
Vol 201 (20) ◽  
Author(s):  
Charles T. Lauhon
Keyword(s):  
Escherichia Coli ◽  
Bacillus Subtilis ◽  
Genomic Context ◽  
Similar Reduction ◽  
Content Type ◽  
E Coli ◽  
Wobble Position ◽  
Fertile Ground ◽  
And Function

ABSTRACT In bacteria, tRNAs that decode 4-fold degenerate family codons and have uridine at position 34 of the anticodon are typically modified with either 5-methoxyuridine (mo5U) or 5-methoxycarbonylmethoxyuridine (mcmo5U). These modifications are critical for extended recognition of some codons at the wobble position. Whereas the alkylation steps of these modifications have been described, genes required for the hydroxylation of U34 to give 5-hydroxyuridine (ho5U) remain unknown. Here, a number of genes in Escherichia coli and Bacillus subtilis are identified that are required for wild-type (wt) levels of ho5U. The yrrMNO operon is identified in B. subtilis as important for the biosynthesis of ho5U. Both yrrN and yrrO are homologs to peptidase U32 family genes, which includes the rlhA gene required for ho5C synthesis in E. coli. Deletion of either yrrN or yrrO, or both, gives a 50% reduction in mo5U tRNA levels. In E. coli, yegQ was found to be the only one of four peptidase U32 genes involved in ho5U synthesis. Interestingly, this mutant shows the same 50% reduction in (m)cmo5U as that observed for mo5U in the B. subtilis mutants. By analyzing the genomic context of yegQ homologs, the ferredoxin YfhL is shown to be required for ho5U synthesis in E. coli to the same extent as yegQ. Additional genes required for Fe-S biosynthesis and biosynthesis of prephenate give the same 50% reduction in modification. Together, these data suggest that ho5U biosynthesis in bacteria is similar to that of ho5C, but additional genes and substrates are required for complete modification. IMPORTANCE Modified nucleotides in tRNA serve to optimize both its structure and function for accurate translation of the genetic code. The biosynthesis of these modifications has been fertile ground for uncovering unique biochemistry and metabolism in cells. In this work, genes that are required for a novel anaerobic hydroxylation of uridine at the wobble position of some tRNAs are identified in both Bacillus subtilis and Escherichia coli. These genes code for Fe-S cluster proteins, and their deletion reduces the levels of the hydroxyuridine by 50% in both organisms. Additional genes required for Fe-S cluster and prephenate biosynthesis and a previously described ferredoxin gene all display a similar reduction in hydroxyuridine levels, suggesting that still other genes are required for the modification.

scholarly journals Molecular Characterization of Commensal Escherichia coli Adapted to Different Compartments of the Porcine Gastrointestinal Tract

2012 ◽  
Vol 78 (19) ◽  
pp. 6799-6803 ◽  
Author(s):  
Sam Abraham ◽  
David M. Gordon ◽  
James Chin ◽  
Huub J. M. Brouwers ◽  
Peter Njuguna ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Gastrointestinal Tract ◽  
Random Amplified Polymorphic Dna ◽  
Content Type ◽  
E Coli ◽  
Plasmid Replicon ◽  
Different Strains ◽  
Different Characteristics

ABSTRACTThe role ofEscherichia colias a pathogen has been the focus of considerable study, while much less is known about it as a commensal and how it adapts to and colonizes different environmental niches within the mammalian gut. In this study, we characterizeEscherichia coliorganisms (n= 146) isolated from different regions of the intestinal tracts of eight pigs (dueodenum, ileum, colon, and feces). The isolates were typed using the method of random amplified polymorphic DNA (RAPD) and screened for the presence of bacteriocin genes and plasmid replicon types. Molecular analysis of variance using the RAPD data showed thatE. coliisolates are nonrandomly distributed among different gut regions, and that gut region accounted for 25% (P< 0.001) of the observed variation among strains. Bacteriocin screening revealed that a bacteriocin gene was detected in 45% of the isolates, with 43% carrying colicin genes and 3% carrying microcin genes. Of the bacteriocins observed (H47, E3, E1, E2, E7, Ia/Ib, and B/M), the frequency with which they were detected varied with respect to gut region for the colicins E2, E7, Ia/Ib, and B/M. The plasmid replicon typing gave rise to 25 profiles from the 13 Inc types detected. Inc F types were detected most frequently, followed by Inc HI1 and N types. Of the Inc types detected, 7 were nonrandomly distributed among isolates from the different regions of the gut. The results of this study indicate that not only may the different regions of the gastrointestinal tract harbor different strains ofE. colibut also that strains from different regions have different characteristics.

scholarly journals Characterization of Multidrug-Resistant Escherichia coli Isolates from Animals Presenting at a University Veterinary Hospital

2011 ◽  
Vol 77 (20) ◽  
pp. 7104-7112 ◽  
Author(s):  
Maria Karczmarczyk ◽  
Yvonne Abbott ◽  
Ciara Walsh ◽  
Nola Leonard ◽  
Séamus Fanning
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Gene Array ◽  
Multidrug Resistant ◽  
Genetic Determinants ◽  
Gene Encoding ◽  
Content Type ◽  
E Coli ◽  
Class 1

ABSTRACTIn this study, we examined molecular mechanisms associated with multidrug resistance (MDR) in a collection ofEscherichia coliisolates recovered from hospitalized animals in Ireland. PCR and DNA sequencing were used to identify genes associated with resistance. Class 1 integrons were prevalent (94.6%) and contained gene cassettes recognized previously and implicated mainly in resistance to aminoglycosides, β-lactams, and trimethoprim (aadA1,dfrA1-aadA1,dfrA17-aadA5,dfrA12-orfF-aadA2,blaOXA-30-aadA1,aacC1-orf1-orf2-aadA1,dfr7). Class 2 integrons (13.5%) contained thedfrA1-sat1-aadA1gene array. The most frequently occurring phenotypes included resistance to ampicillin (97.3%), chloramphenicol (75.4%), florfenicol (40.5%), gentamicin (54%), neomycin (43.2%), streptomycin (97.3%), sulfonamide (98.6%), and tetracycline (100%). The associated resistance determinants detected includedblaTEM,cat,floR,aadB,aphA1,strA-strB,sul2, andtet(B), respectively. TheblaCTX-M-2gene, encoding an extended-spectrum β-lactamase (ESβL), andblaCMY-2, encoding an AmpC-like enzyme, were identified in 8 and 18 isolates, respectively. The mobility of the resistance genes was demonstrated using conjugation assays with a representative selection of isolates. High-molecular-weight plasmids were found to be responsible for resistance to multiple antimicrobial compounds. The study demonstrated that animal-associated commensalE. coliisolates possess a diverse repertoire of transferable genetic determinants. Emergence of ESβLs and AmpC-like enzymes is particularly significant. To our knowledge, theblaCTX-M-2gene has not previously been reported in Ireland.

scholarly journals Characterization of the New AmpC β-Lactamase FOX-8 Reveals a Single Mutation, Phe313Leu, Located in the R2 Loop That Affects Ceftazidime Hydrolysis

2013 ◽  
Vol 57 (10) ◽  
pp. 5158-5161 ◽  
Author(s):  
Francisco José Pérez-Llarena ◽  
Frédéric Kerff ◽  
Laura Zamorano ◽  
María Carmen Fernández ◽  
Maria Luz Nuñez ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Kinetic Analysis ◽  
Clinical Strain ◽  
Single Mutation ◽  
Content Type ◽  
E Coli ◽  
Fold Reduction ◽  
Class C

ABSTRACTA novel class C β-lactamase (FOX-8) was isolated from a clinical strain ofEscherichia coli. The FOX-8 enzyme possessed a unique substitution (Phe313Leu) compared to FOX-3. IsogenicE. colistrains carrying FOX-8 showed an 8-fold reduction in resistance to ceftazidime relative to FOX-3. In a kinetic analysis, FOX-8 displayed a 33-fold reduction inkcat/Kmfor ceftazidime compared to FOX-3. In the FOX family of β-lactamases, the Phe313 residue located in the R2 loop affects ceftazidime hydrolysis and alters the phenotype ofE. colistrains carrying this variant.

scholarly journals Characterization of a Novel Pyranopyridine Inhibitor of the AcrAB Efflux Pump of Escherichia coli

2013 ◽  
Vol 58 (2) ◽  
pp. 722-733 ◽  
Author(s):  
Timothy J. Opperman ◽  
Steven M. Kwasny ◽  
Hong-Suk Kim ◽  
Son T. Nguyen ◽  
Chad Houseweart ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Resistance Nodulation Division ◽  
Rnd Efflux Pumps ◽  
Acrab Efflux Pump

ABSTRACTMembers of the resistance-nodulation-division (RND) family of efflux pumps, such as AcrAB-TolC ofEscherichia coli, play major roles in multidrug resistance (MDR) in Gram-negative bacteria. A strategy for combating MDR is to develop efflux pump inhibitors (EPIs) for use in combination with an antibacterial agent. Here, we describe MBX2319, a novel pyranopyridine EPI with potent activity against RND efflux pumps of theEnterobacteriaceae. MBX2319 decreased the MICs of ciprofloxacin (CIP), levofloxacin, and piperacillin versusE. coliAB1157 by 2-, 4-, and 8-fold, respectively, but did not exhibit antibacterial activity alone and was not active against AcrAB-TolC-deficient strains. MBX2319 (3.13 μM) in combination with 0.016 μg/ml CIP (minimally bactericidal) decreased the viability (CFU/ml) ofE. coliAB1157 by 10,000-fold after 4 h of exposure, in comparison with 0.016 μg/ml CIP alone. In contrast, phenyl-arginine-β-naphthylamide (PAβN), a known EPI, did not increase the bactericidal activity of 0.016 μg/ml CIP at concentrations as high as 100 μM. MBX2319 increased intracellular accumulation of the fluorescent dye Hoechst 33342 in wild-type but not AcrAB-TolC-deficient strains and did not perturb the transmembrane proton gradient. MBX2319 was broadly active againstEnterobacteriaceaespecies andPseudomonas aeruginosa. MBX2319 is a potent EPI with possible utility as an adjunctive therapeutic agent for the treatment of infections caused by Gram-negative pathogens.

scholarly journals Identification and Biochemical Characterization of a Novel Protein Phosphatase 2C-Like Ser/Thr Phosphatase in Escherichia coli

2018 ◽  
Vol 200 (18) ◽  
Author(s):  
Krithika Rajagopalan ◽  
Elizabeth Nagle ◽  
Jonathan Dworkin
Keyword(s):  
Escherichia Coli ◽  
Protein Phosphatase ◽  
Biochemical Characterization ◽  
Regulatory Protein ◽  
Negative Bacterium ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Novel Protein

Regulatory protein phosphorylation is a conserved mechanism of signaling in all biological systems. Recent phosphoproteomic analyses of phylogenetically diverse bacteria, including the model Gram-negative bacteriumEscherichia coli, demonstrate that many proteins are phosphorylated on serine or threonine residues. In contrast to phosphorylation on histidine or aspartate residues, phosphorylation of serine and threonine residues is stable and requires the action of a partner Ser/Thr phosphatase to remove the modification. Although a number of Ser/Thr kinases have been reported inE. coli, no partner Ser/Thr phosphatases have been identified. Here, we biochemically characterize a novel Ser/Thr phosphatase that acts to dephosphorylate a Ser/Thr kinase that is encoded in the same operon.

scholarly journals Molecular Characterization of the EhaG and UpaG Trimeric Autotransporter Proteins from Pathogenic Escherichia coli

2012 ◽  
Vol 78 (7) ◽  
pp. 2179-2189 ◽  
Author(s):  
Makrina Totsika ◽  
Timothy J. Wells ◽  
Christophe Beloin ◽  
Jaione Valle ◽  
Luke P. Allsopp ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Cell Surface ◽  
Specific Binding ◽  
Negative Regulator ◽  
Passenger Domain ◽  
Content Type ◽  
E Coli ◽  
Ecm Proteins

ABSTRACTTrimeric autotransporter proteins (TAAs) are important virulence factors of many Gram-negative bacterial pathogens. A common feature of most TAAs is the ability to mediate adherence to eukaryotic cells or extracellular matrix (ECM) proteins via a cell surface-exposed passenger domain. Here we describe the characterization of EhaG, a TAA identified from enterohemorrhagicEscherichia coli(EHEC) O157:H7. EhaG is a positional orthologue of the recently characterized UpaG TAA from uropathogenicE. coli(UPEC). Similarly to UpaG, EhaG localized at the bacterial cell surface and promoted cell aggregation, biofilm formation, and adherence to a range of ECM proteins. However, the two orthologues display differential cellular binding: EhaG mediates specific adhesion to colorectal epithelial cells while UpaG promotes specific binding to bladder epithelial cells. The EhaG and UpaG TAAs contain extensive sequence divergence in their respective passenger domains that could account for these differences. Indeed, sequence analyses of UpaG and EhaG homologues from severalE. coligenomes revealed grouping of the proteins in clades almost exclusively represented by distinctE. colipathotypes. The expression of EhaG (in EHEC) and UpaG (in UPEC) was also investigated and shown to be significantly enhanced in anhnsisogenic mutant, suggesting that H-NS acts as a negative regulator of both TAAs. Thus, while the EhaG and UpaG TAAs contain some conserved binding and regulatory features, they also possess important differences that correlate with the distinct pathogenic lifestyles of EHEC and UPEC.

scholarly journals Detection and Molecular Characterization of Escherichia coli CTX-M-15 and Klebsiella pneumoniae SHV-12 β-Lactamases from Bovine Mastitis Isolates in the United Kingdom

2013 ◽  
Vol 58 (2) ◽  
pp. 789-794 ◽  
Author(s):  
Dorina Timofte ◽  
Iuliana E. Maciuca ◽  
Nicholas J. Evans ◽  
Helen Williams ◽  
Andrew Wattret ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
United Kingdom ◽  
Klebsiella Pneumoniae ◽  
Bovine Mastitis ◽  
Conjugative Plasmid ◽  
Sensitivity Testing ◽  
Content Type ◽  
E Coli ◽  
The United Kingdom

ABSTRACTRecent reports raised concerns about the role that farm stock may play in the dissemination of extended-spectrum β-lactamase (ESBL)-producing bacteria. This study characterized the ESBLs in twoEscherichia coliand threeKlebsiella pneumoniaesubsp.pneumoniaeisolates from cases of clinical bovine mastitis in the United Kingdom. Bacterial culture and sensitivity testing of bovine mastitic milk samples identified Gram-negative cefpodoxime-resistant isolates, which were assessed for their ESBL phenotypes. Conjugation experiments and PCR-based replicon typing (PBRT) were used for characterization of transferable plasmids.E. coliisolates belonged to sequence type 88 (ST88; determined by multilocus sequence typing) and carriedblaCTX-M-15andblaTEM-1, whileK. pneumoniaesubsp.pneumoniaeisolates carriedblaSHV-12andblaTEM-1. Conjugation experiments demonstrated thatblaCTX-M-15andblaTEM-1were carried on a conjugative plasmid inE. coli, and PBRT identified this to be an IncI1 plasmid. The resistance genes were nontransferable inK. pneumoniaesubsp.pneumoniaeisolates. Moreover, in theE. coliisolates, an association of ISEcp1 and IS26withblaCTX-M-15was found where the IS26element was inserted upstream of both ISEcp1and theblaCTX-Mpromoter, a genetic arrangement highly similar to that described in some United Kingdom human isolates. We report the first cases in Europe of bovine mastitis due toE. coliCTX-M-15 and also of bovine mastitis due toK. pneumoniaesubsp.pneumoniaeSHV-12 β-lactamases in the United Kingdom. We also describe the genetic environment ofblaCTX-M-15and highlight the role that IncI1 plasmids may play in the spread and dissemination of ESBL genes, which have been described in both human and cattle isolates.

scholarly journals Identification and Molecular Characterization of Class 1 Integrons in Multiresistant Escherichia coli Isolates from Poultry Litter

2012 ◽  
Vol 78 (15) ◽  
pp. 5444-5447 ◽  
Author(s):  
Elizabeth Ponce-Rivas ◽  
María-Enriqueta Muñoz-Márquez ◽  
Ashraf A. Khan
Keyword(s):  
Escherichia Coli ◽  
Poultry Litter ◽  
Class 1 Integron ◽  
Content Type ◽  
Gene Cassettes ◽  
E Coli ◽  
Class 1 ◽  
Chicken Litter ◽  
Diverse Origin

ABSTRACTThis study describes the prevalence of arrays of class 1 integron cassettes and Qnr determinants (A, B, and S) in 19 fluoroquinolone-resistantEscherichia coliisolates from chicken litter.qnrSandqnrAwere the predominant genes in these fluoroquinolone-resistant isolates, and an uncommon array ofaacA4-catB3-dfrA1gene cassettes from a class1 integron was found. Additionally,aadA1anddfrA1gene cassettes, encoding resistance to streptomycin and trimethoprim, constituted the most common genes identified and was located on megaplasmids as well on the chromosome. Antibiotic resistance, pulsed-field gel electrophoresis (PFGE), and plasmid data suggest a genetically diverse origin of poultryE. coliisolates.

scholarly journals Genetic Characterization of IncI2 Plasmids CarryingblaCTX-M-55Spreading in both Pets and Food Animals in China

2013 ◽  
Vol 57 (6) ◽  
pp. 2824-2827 ◽  
Author(s):  
Luchao Lv ◽  
Sally R. Partridge ◽  
Liangying He ◽  
Zhenling Zeng ◽  
Dandan He ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genetic Characterization ◽  
Content Type ◽  
E Coli ◽  
Food Animals ◽  
Plasmid Backbone

ABSTRACTpHN1122-1 carryingblaCTX-M-55, from anEscherichia coliisolate from a dog, was completely sequenced. pHN1122-1 has an IncI2 replicon and typical IncI2-associated genetic modules, includingmok/hok-finO-yafA/B,nikABC, and two transfer regions,traandpil, as well as a shufflon.blaCTX-M-55is found within a 3.084-kb ISEcp1transposition unit that includes a fragment of IncA/C plasmid backbone. pHN1122-1 and closely related plasmids were identified in otherE. coliisolates from animals in China.

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