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A mutant L-asparaginase II signal peptide improves the secretion of recombinant cyclodextrin glucanotransferase and the viability of Escherichia coli

Ismail NF, Hamdan S, Mahadi NM, Murad AM, Rabu A, Bakar FD, et al.

Biotechnol Lett, 2011 May;33(5):999-1005.
PMID: 21234789 DOI: 10.1007/s10529-011-0517-8

L-Asparaginase II signal peptide was used for the secretion of recombinant cyclodextrin glucanotransferase (CGTase) into the periplasmic space of E. coli. Despite its predominant localisation in the periplasm, CGTase activity was also detected in the extracellular medium, followed by cell lysis. Five mutant signal peptides were constructed to improve the periplasmic levels of CGTase. N1R3 is a mutated signal peptide with the number of positively charged amino acid residues in the n-region increased to a net charge of +5. This mutant peptide produced a 1.7-fold enhancement of CGTase activity in the periplasm and significantly decreased cell lysis to 7.8% of the wild-type level. The formation of intracellular inclusion bodies was also reduced when this mutated signal peptide was used as judged by SDS-PAGE. Therefore, these results provide evidence of a cost-effective means of expression of recombinant proteins in E. coli.

Matched MeSH terms: Escherichia coli/enzymology*
Fulltext A secondary mode of action of polymyxins against Gram-negative bacteria involves the inhibition of NADH-quinone oxidoreductase activity

Deris ZZ, Akter J, Sivanesan S, Roberts KD, Thompson PE, Nation RL, et al.

J Antibiot (Tokyo), 2014 Feb;67(2):147-51.
PMID: 24169795 DOI: 10.1038/ja.2013.111

Polymyxin B and colistin were examined for their ability to inhibit the type II NADH-quinone oxidoreductases (NDH-2) of three species of Gram-negative bacteria. Polymyxin B and colistin inhibited the NDH-2 activity in preparations from all of the isolates in a concentration-dependent manner. The mechanism of NDH-2 inhibition by polymyxin B was investigated in detail with Escherichia coli inner membrane preparations and conformed to a mixed inhibition model with respect to ubiquinone-1 and a non-competitive inhibition model with respect to NADH. These suggest that the inhibition of vital respiratory enzymes in the bacterial inner membrane represents one of the secondary modes of action for polymyxins.

Matched MeSH terms: Escherichia coli/enzymology
Fulltext Antibacterial Mode of Action of Cinnamomum verum Bark Essential Oil, Alone and in Combination with Piperacillin, Against a Multi-Drug-Resistant Escherichia coli Strain

Yap PS, Krishnan T, Chan KG, Lim SH

J Microbiol Biotechnol, 2015 Aug;25(8):1299-306.
PMID: 25381741 DOI: 10.4014/jmb.1407.07054

This study aimed to investigate the mechanism of action of the cinnamon bark essential oil (CB), when used singly and also in combination with piperacillin, for its antimicrobial and synergistic activity against beta-lactamase TEM-1 plasmid-conferred Escherichia coli J53 R1. Viable count of this combination showed a complete killing profile at 20 h and further confirmed its synergistic effect by reducing the bacteria cell numbers. Analysis on the stability of treated cultures for cell membrane permeability by CB when tested against sodium dodecyl sulfate revealed that the bacterial cell membrane was disrupted by the essential oils. Scanning electron microscopy observation and bacterial surface charge measurement also revealed that CB causes irreversible membrane damage and reduces the bacterial surface charge. In addition, bioluminescence expression of Escherichia coli [pSB1075] and E. coli [pSB401] by CB showed reduction, indicating the possibility of the presence of quorum sensing (QS) inhibitors. Gas-chromatography and mass spectrometry of the essential oil of Cinnamomum verum showed that trans-cinnamaldehyde (72.81%), benzyl alcohol (12.5%), and eugenol (6.57%) were the major components in the essential oil. From this study, CB has the potential to reverse E. coli J53 R1 resistance to piperacillin through two pathways; modification in the permeability of the outer membrane or bacterial QS inhibition.

Matched MeSH terms: Escherichia coli/enzymology
Antibiotic resistance patterns in nosocomial gram-negative bacterial infections in units with heavy antibiotic usage

Ariffin H, Navaratnam P, Kee TK, Balan G

J Trop Pediatr, 2004 Feb;50(1):26-31.
PMID: 14984166

The pattern of antibiotic resistance amongst gram-negative bacteria (GNB) in paediatric units, which have heavy empirical usage of broad-spectrum antibiotics, was studied prospectively over a 6-month period. A total of 200 consecutive, non-duplicate gram-negative isolates were obtained from 109 patients admitted to intensive care and oncology units in two hospitals. The commonest isolates were Klebsiella spp (36.5 per cent) and Pseudomonas (20.0 per cent). The isolates showed lower susceptibility rates to the third-generation cephalosporins (47-62 per cent) compared with cefepime (91 per cent), imipenem (90 per cent) and ciprofloxacin (99 per cent). Fifty-four (52.8 per cent) Klebsiella and Escherichia coli isolates were determined to be extended-spectrum beta-lactamase (ESBL) producing strains. Antibiotics found to be effective against ESBL-producers were imipenem and ciprofloxacin. The high resistance rate amongst GNB to third-generation cephalosporins is a likely consequence of heavy empirical usage of this group of antibiotics. The carbapenems and quinolones remain useful agents in the management of patients admitted to these units.

Matched MeSH terms: Escherichia coli/enzymology
Bacteriocin release protein-mediated secretory expression of recombinant chalcone synthase in Escherichia coli

Zakaria II, Rahman RN, Salleh AB, Basri M

Appl Biochem Biotechnol, 2011 Sep;165(2):737-47.
PMID: 21633820 DOI: 10.1007/s12010-011-9292-1

Flavonoids are secondary metabolites synthesized by plants shown to exhibit health benefits such as anti-inflammatory, antioxidant, and anti-tumor effects. Thus, due to the importance of this compound, several enzymes involved in the flavonoid pathway have been cloned and characterized in Escherichia coli. However, the formation of inclusion bodies has become a major disadvantage of this approach. As an alternative, chalcone synthase from Physcomitrella patens was secreted into the medium using a bacteriocin release protein expression vector. Secretion of P. patens chalcone synthase into the culture media was achieved by co-expression with a psW1 plasmid encoding bacteriocin release protein in E. coli Tuner (DE3) plysS. The optimized conditions, which include the incubation of cells for 20 h with 40 ng/ml mitomycin C at OD(600) induction time of 0.5 was found to be the best condition for chalcone synthase secretion.

Matched MeSH terms: Escherichia coli/enzymology
Fulltext Characterization of multidrug resistant ESBL-producing Escherichia coli isolates from hospitals in Malaysia

Lim KT, Yasin R, Yeo CC, Puthucheary S, Thong KL

J Biomed Biotechnol, 2009;2009:165637.
PMID: 19672454 DOI: 10.1155/2009/165637

The emergence of Escherichia coli that produce extended spectrum beta-lactamases (ESBLs) and are multidrug resistant (MDR) poses antibiotic management problems. Forty-seven E. coli isolates from various public hospitals in Malaysia were studied. All isolates were sensitive to imipenem whereas 36 were MDR (resistant to 2 or more classes of antibiotics). PCR detection using gene-specific primers showed that 87.5% of the ESBL-producing E. coli harbored the blaTEM gene. Other ESBL-encoding genes detected were blaOXA, blaSHV, and blaCTX-M. Integron-encoded integrases were detected in 55.3% of isolates, with class 1 integron-encoded intI1 integrase being the majority. Amplification and sequence analysis of the 5'CS region of the integrons showed known antibiotic resistance-encoding gene cassettes of various sizes that were inserted within the respective integrons. Conjugation and transformation experiments indicated that some of the antibiotic resistance genes were likely plasmid-encoded and transmissible. All 47 isolates were subtyped by PFGE and PCR-based fingerprinting using random amplified polymorphic DNA (RAPD), repetitive extragenic palindromes (REPs), and enterobacterial repetitive intergenic consensus (ERIC). These isolates were very diverse and heterogeneous. PFGE, ERIC, and REP-PCR methods were more discriminative than RAPD in subtyping the E. coli isolates.

Matched MeSH terms: Escherichia coli/enzymology*
Cloning of glyceraldehyde-3-phosphate dehydrogenase from an Antarctic psychrophilic bacterium by inverse and splinkerette PCR

Too WC, Liew YC, Few LL

J Basic Microbiol, 2008 Oct;48(5):430-5.
PMID: 18759222 DOI: 10.1002/jobm.200800008

Psychrophiles are organisms that thrive in cold environments. One of the strategies for their cold adaptation is the ability to synthesize cold-adapted enzymes. These enzymes usually display higher catalytic efficiency and thermolability at lower temperatures compared to their mesophilic and thermophilic counterparts. In this work, a psychrophilic bacterium codenamed pi9 was selected for the cloning of the gene encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH), an enzyme in the glycolytic pathway. Here, the cloning of an 1,113 bp fragment of GAPDH gene which covers the 1,002 bp open reading frame by using multiple PCR steps is described. The partial sequence of this gene was PCR amplified by using degenerate primers followed by the cloning of the flanking sequences by inverse and splinkerette PCR techniques. The success in cloning the GAPDH gene by PCR has bypassed the more time consuming genomic library construction and screening method. The full length GAPDH protein was subsequently expressed in E. coli, purified as His-tag protein and confirmed to be catalytically active. This work demonstrated the use of multiple PCR techniques to clone a gene based solely on sequence comparison. It also laid the foundation for further biochemical and structural characterizations of GAPDH from a psychrophilic bacterium by providing a highly purified recombinant protein sample.

Matched MeSH terms: Escherichia coli/enzymology
Cloning of high activity xylanase gene from Bacillus pumilus PJ19

Hamzah A, Abdulrashid N

J. Biochem. Mol. Biol. Biophys., 2002 Oct;6(5):365-9.
PMID: 12385974

The xylanase gene from Bacillus pumilus PJ19 amplified by polymerase chain reaction (PCR) was cloned into pCRII vector and transformed into Escherichia coli strain INValphaF'. Starting from an ATG as an initiator codon, an open reading frame coding for 202 amino acids was obtained. The recombinant xylanase sequence showed a 96% homology with the xylanase sequence from B. pumilus IPO strain and had an estimated molecular weight of 22,474. Xylanase activity expressed by E. coli INValphaF' harboring the cloned gene was located primarily in the cytoplasmic fraction.

Matched MeSH terms: Escherichia coli/enzymology
Concerted inhibition of NADP+-specific isocitrate dehydrogenase by oxalacetate and glyoxylate. I. Oxalomalate formation and stability, and nature of the enzyme inhibition

Johanson RA, Reeves HC

Biochim. Biophys. Acta, 1977 Jul 08;483(1):24-34.
PMID: 18195

Oxalacetate and glyoxylate are each weak inhibitors of NADP+-specific isocitrate dehydrogenase (threo-DS-isocitrate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.42)9 Together, however, they act in a concerted manner and strongly inhibit the enzyme. The rates of formation and dissociation of the enzyme inhibitor complex, and the rate of formation and the stability of the aldol condensation product of oxalacetate and glyoxylate, oxalomalate, were examined. The data obtained do not support the often suggested possibility that oxalomalate, per se, formed non-enzymatically in isocitrate dehydrogenase assay mixtures containing oxalacetate and glyoxylate, is responsible for the observed inhibition of the enzyme. Rather, the data presented in this communication suggest that oxalacetate binds to the enzyme first, and that the subsequent binding of glyoxylate leads to the formation of a catalytically inactive enzyme-inhibitor complex.

Matched MeSH terms: Escherichia coli/enzymology
Fulltext Detection and characterization of ESBL-producing Enterobacteriaceae from the gut of healthy chickens, Gallus gallus domesticus in rural Nepal: Dominance of CTX-M-15-non-ST131 Escherichia coli clones

Hosuru Subramanya S, Bairy I, Nayak N, Amberpet R, Padukone S, Metok Y, et al.

PLoS One, 2020;15(5):e0227725.
PMID: 32469888 DOI: 10.1371/journal.pone.0227725

The surge in the prevalence of drug-resistant bacteria in poultry is a global concern as it may pose an extended threat to humans and animal health. The present study aimed to investigate the colonization proportion of extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Enterobacteriaceae (EPE and CPE, respectively) in the gut of healthy poultry, Gallus gallus domesticus in Kaski district of Western Nepal. Total, 113 pooled rectal swab specimens from 66 private household farms and 47 commercial poultry farms were collected by systematic random sampling from the Kaski district in western Nepal. Out of 113 pooled samples, 19 (28.8%) samples from 66 backyard farms, and 15 (31.9%) from 47 commercial broiler farms were positive for EPE. Of the 38 EPE strains isolated from 34 ESBL positive rectal swabs, 31(81.6%) were identified as Escherichia coli, five as Klebsiella pneumoniae (13.2%), and one each isolate of Enterobacter species and Citrobacter species (2.6%). Based on genotyping, 35/38 examined EPE strains (92.1%) were phylogroup-1 positive, and all these 35 strains (100%) had the CTX-M-15 gene and strains from phylogroup-2, and 9 were of CTX-M-2 and CTX-M-14, respectively. Among 38 ESBL positive isolates, 9 (23.7%) were Ambler class C (Amp C) co-producers, predominant were of DHA, followed by CIT genes. Two (6.5%) E. coli strains of ST131 belonged to clade C, rest 29/31 (93.5%) were non-ST131 E. coli. None of the isolates produced carbapenemase. Twenty isolates (52.6%) were in-vitro biofilm producers. Univariate analysis showed that the odd of ESBL carriage among commercial broilers were 1.160 times (95% CI 0.515, 2.613) higher than organically fed backyard flocks. This is the first study in Nepal, demonstrating the EPE colonization proportion, genotypes, and prevalence of high-risk clone E. coli ST131 among gut flora of healthy poultry. Our data indicated that CTX-M-15 was the most prevalent ESBL enzyme, mainly associated with E. coli belonging to non-ST131clones and the absence of carbapenemases.

Matched MeSH terms: Escherichia coli/enzymology
Enhanced secretory production of hemolysin-mediated cyclodextrin glucanotransferase in Escherichia coli by random mutagenesis of the ABC transporter system

Low KO, Mahadi NM, Abdul Rahim R, Rabu A, Abu Bakar FD, Abdul Murad AM, et al.

J Biotechnol, 2010 Dec;150(4):453-9.
PMID: 20959127 DOI: 10.1016/j.jbiotec.2010.10.001

The hemolysin transport system was found to mediate the release of cyclodextrin glucanotransferase (CGTase) into the extracellular medium when it was fused to the C-terminal 61 amino acids of HlyA (HlyAs(61)). To produce an improved-secretion variant, the hly components (hlyAs, hlyB and hlyD) were engineered by directed evolution using error-prone PCR. Hly mutants were screened on solid LB-starch plate for halo zone larger than the parent strain. Through screening of about 1 × 10(4) Escherichia coli BL21(DE3) transformants, we succeeded in isolating five mutants that showed a 35-217% increase in the secretion level of CGTase-HlyAs(61) relative to the wild-type strain. The mutation sites of each mutant were located at HlyB, primarily along the transmembrane domain, implying that the corresponding region was important for the improved secretion of the target protein. In this study we describe the finding of novel site(s) of HlyB responsible for enhancing secretion of CGTase in E. coli.

Matched MeSH terms: Escherichia coli/enzymology*
Exhaustive study of the novel hyper alkalophil, thermostable, and chelator resistant metalloprotease

Samie N, Haerian B, Muniandy S, Green D, Ashouri M

Appl Biochem Biotechnol, 2015 Apr;175(7):3397-417.
PMID: 25820296 DOI: 10.1007/s12010-015-1513-6

Our newly discovered metalloprotease, designated as ALP NS12 was selected using gelatin agar plates with incubation at 100 °C. Subcloning of the fragments in to pUC118 to make E. coli HB101 (pPEMP01NS) with following two-step chromatography using diethylaminoethyl sepharose (DEAE-sepharose) and Sephadex G-100 columns to purify 97-kDa expressed enzyme was performed. Although activity of immobilized ALP NS12 on glass surface was established at temperatures between 70 and 120 °C and pH ranges 4.0-13.0, the optimum temperature and pH were achieved at 100 °C and 11.0, respectively. Enhancement of enzyme activity was obtained in the presence of 5 mM MnCl2 (91 %), CaCl2 (357 %), FeCl2 (175 %), MgCl2 (94 %), ZnCl2 (412 %), NiCl (86 %), NaCl (239 %), and Na-sulfate (81 %) while inhibition was observed with EDTA (5 mM), PMSF (3 mM), urea (8 M), and SDS (1 %) at 65, 37, 33, and 42 %, respectively. Consequently, the enzyme was well analyzed using crystallography and protein modeling. ALP NS12 can be applied in industrial processes at extreme temperatures and under highly basic conditions, chelators, and detergents.

Matched MeSH terms: Escherichia coli/enzymology
Extended-spectrum beta-lactam resistance due to AmpC hyperproduction and CMY-2 coupled with the loss of OMPK35 in Malaysian strains of Escherichia coli and Klebsiella pneumoniae

Palasubramaniam S, Subramaniam G, Muniandy S, Parasakthi N

Microb Drug Resist, 2007;13(3):186-90.
PMID: 17949305

In this report, we describe the detection of AmpC and CMY-2 beta-lactamases with the loss of OmpK35 porin among seven sporadic strains of ceftazidime-resistant Klebsiella pneumoniae and ceftazidime-resistant Escherichia coli. Cefoxitin, which was used as a marker of resistance toward 7-alpha-methoxy-cephalosporins, exhibited high minimum inhibitory concentration (MIC) values ranging between 128 microg/ml and >256 microg/ml in all the strains. The presence of hyperproducing AmpC enzymes was indicated by the positive three-dimensional test. Isoelectric focusing (IEF) study confirmed the presence of AmpC enzymes in all the strains. The ampC gene was detected by PCR in all the strains and confirmed by DNA sequencing. Large plasmids in all the strains, ranging from 60 kb to 150 kb in size, most likely encode the ampC gene. Two E. coli strains out of the seven strains showed positive amplification of the bla(CMY-2) gene, an AmpC variant, and was confirmed by DNA sequence analyses. DNA hybridization confirmed the bla(CMY-2) gene to be plasmid-mediated in both of these strains. However, one of these two strains also mediated a chromosomal CMY gene. All the strains showed an absence of OmpK35 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS/PAGE) and was confirmed by western blot analyses using raised polyclonal anti-OmpK35 antiserum. This suggests that, apart from CMY production, absence of OmpK35 porin also contributed to cefoxitin resistance resulting in extended-spectrum beta-lactam resistance among these isolates.

Matched MeSH terms: Escherichia coli/enzymology
Improvement of cyclodextrin glycosyltransferase gene expression in Escherichia coli by insertion of regulatory sequences involved in the promotion of RNA transcription

Ramli N, Abd-Aziz S, Alitheen NB, Hassan MA, Maeda T

Mol Biotechnol, 2013 Jul;54(3):961-8.
PMID: 23338983 DOI: 10.1007/s12033-013-9647-7

Regulation of RNA transcription in controlling the expression of genes at promoter and terminator regions is crucial as the interaction of RNA polymerase occurred at both sites. Gene encoding cyclodextrin glycosyltransferase (CGTase) from Bacillus sp. NR5 UPM isolated in the previous study was used for further construction of pTZCGT-SS, pTZCGT-BS and pTZCGT-BT expression systems for enhancement of CGTase production. The putative promoter regions, -35 and -10 sequences were found in the upstream of the mature gene start codon. Whereas, long inverted repeats sequences which can form a stable stem and loop structure was found downstream of the open reading frame (ORF) of Bacillus sp. NR5 UPM CGTase. The construction of E. coli strain harbouring pTZCGT-BS showed increment of 3.2-fold in CGTase activity compared to the wild type producer. However, insertion of terminator downstream of CGTase gene in E. coli strain harbouring pTZCGT-BT only resulted in 4.42 % increment of CGTase production compared to E. coli strain containing pTZCGT-BS, perhaps due to low intrinsic termination efficiency. Thus, it is suggested that the insertion of the putative promoter regions upstream of the coding sequence for the construction of CGTase expression system will further enhance in the recombinant enzyme production.

Matched MeSH terms: Escherichia coli/enzymology
Inhibition of lysosomal vacuolar proton pump down-regulates cellular acidification and enhances E. coli bactofection efficiency

Akinsola RO, Lee CW, Sim EUH, Narayanan K

Anal Biochem, 2021 03 01;616:114088.
PMID: 33358938 DOI: 10.1016/j.ab.2020.114088

Endosomal escape is considered a crucial barrier that needs to be overcome by integrin-mediated E. coli for gene delivery into mammalian cells. Bafilomycin, a potent inhibitor of the H+ proton pump commonly employed to lower endosomal pH, was evaluated as part of the E. coli protocol during delivery. We found an increase in green fluorescent protein expression up 6.9, 3.2, 5.0, 2.8, and 4.5 fold in HeLa, HEK-293, A549, HT1080, and MCF-7 respectively, compared to untreated cells. Our result showed for the first time that Inhibition of lysosomal V-ATPase enhances E. coli efficiency.

Matched MeSH terms: Escherichia coli/enzymology*
Fulltext Lineage-Specific Methyltransferases Define the Methylome of the Globally Disseminated Escherichia coli ST131 Clone

Forde BM, Phan MD, Gawthorne JA, Ashcroft MM, Stanton-Cook M, Sarkar S, et al.

mBio, 2015 Nov 17;6(6):e01602-15.
PMID: 26578678 DOI: 10.1128/mBio.01602-15

Escherichia coli sequence type 131 (ST131) is a clone of uropathogenic E. coli that has emerged rapidly and disseminated globally in both clinical and community settings. Members of the ST131 lineage from across the globe have been comprehensively characterized in terms of antibiotic resistance, virulence potential, and pathogenicity, but to date nothing is known about the methylome of these important human pathogens. Here we used single-molecule real-time (SMRT) PacBio sequencing to determine the methylome of E. coli EC958, the most-well-characterized completely sequenced ST131 strain. Our analysis of 52,081 methylated adenines in the genome of EC958 discovered three (m6)A methylation motifs that have not been described previously. Subsequent SMRT sequencing of isogenic knockout mutants identified the two type I methyltransferases (MTases) and one type IIG MTase responsible for (m6)A methylation of novel recognition sites. Although both type I sites were rare, the type IIG sites accounted for more than 12% of all methylated adenines in EC958. Analysis of the distribution of MTase genes across 95 ST131 genomes revealed their prevalence is highly conserved within the ST131 lineage, with most variation due to the presence or absence of mobile genetic elements on which individual MTase genes are located.
IMPORTANCE: DNA modification plays a crucial role in bacterial regulation. Despite several examples demonstrating the role of methyltransferase (MTase) enzymes in bacterial virulence, investigation of this phenomenon on a whole-genome scale has remained elusive until now. Here we used single-molecule real-time (SMRT) sequencing to determine the first complete methylome of a strain from the multidrug-resistant E. coli sequence type 131 (ST131) lineage. By interrogating the methylome computationally and with further SMRT sequencing of isogenic mutants representing previously uncharacterized MTase genes, we defined the target sequences of three novel ST131-specific MTases and determined the genomic distribution of all MTase target sequences. Using a large collection of 95 previously sequenced ST131 genomes, we identified mobile genetic elements as a major factor driving diversity in DNA methylation patterns. Overall, our analysis highlights the potential for DNA methylation to dramatically influence gene regulation at the transcriptional level within a well-defined E. coli clone.

Matched MeSH terms: Uropathogenic Escherichia coli/enzymology*
Novel Ag/cellulose-doped CeO2 quantum dots for efficient dye degradation and bactericidal activity with molecular docking study

Ikram M, Hayat S, Imran M, Haider A, Naz S, Ul-Hamid A, et al.

Carbohydr Polym, 2021 Oct 01;269:118346.
PMID: 34294353 DOI: 10.1016/j.carbpol.2021.118346

In the present study, the novel Ag/cellulose nanocrystal (CNC)-doped CeO2 quantum dots (QDs) with highly efficient catalytic performance were synthesized using one pot co-precipitation technique, which were then applied in the degradation of methylene blue and ciprofloxacin (MBCF) in wastewater. Catalytic activity against MBCF dye was significantly reduced (99.3%) for (4%) Ag dopant concentration in acidic medium. For Ag/CNC-doped CeO2 vast inhibition domain of G-ve was significantly confirmed as (5.25-11.70 mm) and (7.15-13.60 mm), while medium- to high-concentration of CNC levels were calculated for G + ve (0.95 nm, 1.65 mm), respectively. Overall, (4%) Ag/CNC-doped CeO2 revealed significant antimicrobial activity against G-ve relative to G + ve at both concentrations, respectively. Furthermore, in silico molecular docking studies were performed against selected enzyme targets dihydrofolate reductase (DHFR), dihydropteroate synthase (DHPS), and DNA gyrase belonging to folate and nucleic acid biosynthetic pathway, respectively to rationalize possible mechanism behind bactericidal potential of CNC-CeO2 and Ag/CNC-CeO2.

Matched MeSH terms: Escherichia coli/enzymology
Fulltext Prevalence and association of pks+ Escherichia coli with colorectal cancer in patients at the University Malaya Medical Centre, Malaysia

Iyadorai T, Mariappan V, Vellasamy KM, Wanyiri JW, Roslani AC, Lee GK, et al.

PLoS One, 2020;15(1):e0228217.
PMID: 31990962 DOI: 10.1371/journal.pone.0228217

Escherichia coli (E. coli) from the B2 phylogenetic group is implicated in colorectal cancer (CRC) as it possesses a genomic island, termed polyketide synthetase (pks), which codes for the synthesis of colibactin, a genotoxin that induces DNA damage, cell cycle arrest, mutations and chromosomal instability in eukaryotic cells. The aim of this study was to detect and compare the prevalence of E. coli expressing pks (pks+ E. coli) in CRC patients and healthy controls followed by investigating the virulence triggered by pks+ E. coli using an in-vitro model. Mucosal colon tissues were collected and processed to determine the presence of pks+ E. coli. Thereafter, primary colon epithelial (PCE) and colorectal carcinoma (HCT116) cell lines were used to detect cytopathic response to the isolated pks+ E. coli strains. Our results showed 16.7% and 4.3% of CRC and healthy controls, respectively were pks+ E. coli. Further, PCE displayed syncytia and cell swelling and HCT116 cells, megalocytosis, in response to treatment with the isolated pks+ E. coli strains. In conclusion, pks+ E. coli was more often isolated from tissue of CRC patients compared to healthy individuals, and our in-vitro assays suggest these isolated strains may be involved in the initiation and development of CRC.

Matched MeSH terms: Escherichia coli/enzymology*
Rational design of bis-indolylmethane-oxadiazole hybrids as inhibitors of thymidine phosphorylase

Taha M, Rashid U, Imran S, Ali M

Bioorg Med Chem, 2018 07 23;26(12):3654-3663.
PMID: 29853339 DOI: 10.1016/j.bmc.2018.05.046

Inhibition of Thymidine phosphorylase (TP) is continuously studied for the design and development of new drugs for the treatment of neoplastic diseases. As a part of our effort to identify TP inhibitors, we performed a structure-based virtual screening (SBVS) of our compound collection. Based on the insights gained from structures of virtual screening hits, a scaffold was designed using 1,3,4-oxadiazole as the basic structural feature and SAR studies were carried out for the optimization of this scaffold. Twenty-five novel bis-indole linked 1,3,4-oxadiazoles (7-31) were designed, synthesized and tested in vitro against E. coli TP (EcTP). Compound 7 emerged as potent TP inhibitor with an IC50 value of 3.50 ± 0.01 μM. Docking studies were carried out using GOLD software on thymidine phosphorylase from human (hTP) and E. coli (EcTP). Various hydrogen bonding, hydrophobic interactions, and π-π stacking were observed between designed molecules and the active site amino acid residues of the studied enzymes.

Matched MeSH terms: Escherichia coli/enzymology
Resistance to extended-spectrum beta-lactams by the emergence of SHV-12 and the loss of OmpK35 in Klebsiella pneumoniae and Escherichia coli in Malaysia

Palasubramaniam S, Muniandy S, Navaratnam P

J Microbiol Immunol Infect, 2009 Apr;42(2):129-33.
PMID: 19597644

In addition to beta-lactamase production, loss of porins confers resistance to extended-spectrum beta-lactams in Klebsiella pneumoniae and Escherichia coli infection. This study describes the detection of SHV-12 extended-spectrum beta-lactamase (ESBL) subtype and the loss of OmpK35 porin in 4 strains of K. pneumoniae and E. coli.

Matched MeSH terms: Escherichia coli/enzymology*

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