scholarly journals Degradation of Chlorinated Dibenzofurans and Dibenzo-p-Dioxins by Two Types of Bacteria Having Angular Dioxygenases with Different Features

2001 ◽  
Vol 67 (8) ◽  
pp. 3610-3617 ◽  
Author(s):  
Hiroshi Habe ◽  
Jin-Sung Chung ◽  
Jong-Hoon Lee ◽  
Kano Kasuga ◽  
Takako Yoshida ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Wild Type ◽  
Extradiol Dioxygenase ◽  
Angular Dioxygenation ◽  
Type Strains ◽  
Angular Dioxygenase ◽  
Strain Ca10 ◽  
Chlorinated Dibenzofurans

ABSTRACT Two kinds of bacteria having different-structured angular dioxygenases—a dibenzofuran (DF)-utilizing bacterium,Terrabacter sp. strain DBF63, and a carbazole (CAR)-utilizing bacterium, Pseudomonas sp. strain CA10—were investigated for their ability to degrade some chlorinated dibenzofurans (CDFs) and chlorinated dibenzo-p-dioxins (CDDs) (or, together, CDF/Ds) using either wild-type strains or recombinant Escherichia coli strains. First, it was shown that CAR 1,9a-dioxygenase (CARDO) catalyzed angular dioxygenation of all mono- to triCDF/Ds investigated in this study, but DF 4,4a-dioxygenase (DFDO) did not degrade 2,7-diCDD. Secondly, degradation of CDF/Ds by the sets of three enzymes (angular dioxygenase, extradiol dioxygenase, and meta-cleavage compound hydrolase) was examined, showing that these enzymes in both strains were able to convert 2-CDF to 5-chlorosalicylic acid but not other tested substrates to the corresponding chlorosalicylic acid (CSA) or chlorocatechol (CC). Finally, we tested the potential of both wild-type strains for cooxidation of CDF/Ds and demonstrated that both strains degraded 2-CDF, 2-CDD, and 2,3-diCDD to the corresponding CSA and CC. We investigated the sites for the attack of angular dioxygenases in each CDF/D congener, suggesting the possibility that the angular dioxygenation of 2-CDF, 2-CDD, 2,3-diCDD, and 1,2,3-triCDD (10 ppm each) by both DFDO and CARDO occurred mainly on the nonsubstituted aromatic nuclei.

scholarly journals Natural Genetic Transformation of Clinical Isolates of Escherichia coli in Urine and Water

2002 ◽  
Vol 68 (1) ◽  
pp. 440-443 ◽  
Author(s):  
Markus Woegerbauer ◽  
Bernard Jenni ◽  
Florian Thalhammer ◽  
Wolfgang Graninger ◽  
Heinz Burgmann
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Current Knowledge ◽  
Antibiotic Resistance Genes ◽  
Aquatic Environments ◽  
Wild Type ◽  
E Coli ◽  
Naturally Occurring ◽  
Natural Genetic Transformation ◽  
Type Strains

ABSTRACT Transfer of plasmid-borne antibiotic resistance genes in Escherichia coli wild-type strains is possible by transformation under naturally occurring conditions in oligotrophic, aquatic environments containing physiologic concentrations of calcium. In contrast, transformation is suppressed in nitrogen-rich body fluids like urine, a common habitat of uropathogenic strains. Current knowledge indicates that transformation of these E. coli wild-type strains is of no relevance for the acquisition of resistance in this clinically important environment.

A Stable 44S Intermediate in the Autodigestion of 50S Ribosomal Subunits

1971 ◽  
Vol 29 ◽  
pp. 430-431
Author(s):  
John H. Nisbet ◽  
Henry S. Slayter
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Ribosomal Rna ◽  
Gel Electrophoresis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Ribosomal Subunit ◽  
Wild Type ◽  
Ribosomal Subunits ◽  
Type Strains

Wild - type strains of Escherichia coli are known to contain as many as four endogenous nucleases (Ref. 1). These are commonly found associated with the ribosomes after extraction from the cell, but may be removed, with the exception of RNase IV, by washing the ribosomes in NH4Cl (at 0.2 M and higher concentrations). We have examined the effect of these nucleases on the 50S ribosomal subunit of one wild-type strain, K12 (Hfr 3000), by incubating the unwashed particles at 37° in the presence of varying magnesium concentrations.At 10-4 molar magnesium (slower at 10-3 molar), the 50S particle is converted to a species sedimenting at about 44S. About 20% of the total O.D260 is liberated at the same time. Continued incubation leads to the release of more O.D260 material while the RNA remaining in the 44S (Fig. 1) particle is progressively cleaved, eventually to the point where it consists of one principal fragment of molecular weight 0.42 x 106 daltons and several lesser fragments. The ribosomal RNA and proteins have been characterized by acrylamide gel electrophoresis.

Colicins G and H and their host strains

1991 ◽  
Vol 37 (10) ◽  
pp. 751-757 ◽  
Author(s):  
D. E. Bradley
Keyword(s):  
Escherichia Coli ◽  
Key Words ◽  
Side Chains ◽  
Human Origin ◽  
Wild Type ◽  
E Coli ◽  
Molecular Weights ◽  
Protein Receptors ◽  
Type Strains ◽  
Host Strains

Escherichia coli strains CA46(pColG) and CA58(pColH) each apparently synthesized two generally similar bactericidal colicin proteins whose molecular weights were approximately 5 500 and 100 000. These proteins were more resistant to trypsin than representative colicins A, D, E1, and V. The smooth wild-type strains harbouring plasmids pColG and pColH were serotyped O169:NM and O30:NM, respectively, being typically associated with nonpathogenic E. coli of human origin. Rough and semirough variants, which were selected using resistance to novobiocin, were intrinsically insensitive to almost as many colicins (10 tested) as their parents. For this reason the wild-type strains would not be useful for identifying colicins G and H on the basis of immunity. The O antigenic side chains of both wild-type strains shielded three of the six bacteriophage protein receptors tested. Key words: colicin, protein, plasmid, O antigen, bacteriophage.

scholarly journals Acquisition and Maintenance of Enterotoxin Plasmids in Wild-type Strains of Escherichia coli

Microbiology ◽  
1983 ◽  
Vol 129 (10) ◽  
pp. 3111-3120 ◽  
Author(s):  
S. M. Scotland ◽  
N. P. Day ◽  
B. Rowe
Keyword(s):  
Escherichia Coli ◽  
Wild Type ◽  
Type Strains

Phase variation of F1651 (Prs-like) fimbriae from Escherichia coli causing septicaemia in animals

2000 ◽  
Vol 46 (12) ◽  
pp. 1101-1107 ◽  
Author(s):  
Josée Harel ◽  
France Daigle ◽  
Céline Forget ◽  
Marie-Catherine Tessier ◽  
Cécile Crost ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Regulatory Region ◽  
Phase Variation ◽  
Immunofluorescence Staining ◽  
Wild Type ◽  
Young Pigs ◽  
Dam Methylation ◽  
Structural Subunit ◽  
Type Strains

Escherichia coli O115:F165 strains are associated with septicaemia in young pigs and synthesize fimbriae involved in virulence, designated as F1651. F1651 fimbriae belong to the P fimbrial family and are encoded by the foo gene cluster. The foo regulatory region of strain 5131 possesses characteristics similar to that of members of the P regulatory family, including papI and papB homologues, and two GATC sites separated by 102 bp, targets of differential Dam methylation. In wild-type strains, the synthesis of F1651 is repressed by leucine and the fimbriae undergo phase variation. Immunofluorescence staining showed that phase variation of F1651 results in a majority of cells (98%) in the ON phase, in contrast with phase variation of other members of this regulatory family, for which the majority of the cells are in the OFF state. Using a translational fusion in strain 5131 between phoA and fooA, encoding for the major structural subunit of F1651, it was shown that leucine inhibits the OFF to ON switch and modulates the basal transcription of the foo operon.Key words: Escherichia coli, fimbriae, phase variation, regulation, septicaemia.

scholarly journals Effect on solute size on diffusion rates through the transmembrane pores of the outer membrane of Escherichia coli.

1981 ◽  
Vol 77 (2) ◽  
pp. 121-135 ◽  
Author(s):  
H Nikaido ◽  
E Y Rosenberg
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Specific Class ◽  
Wild Type ◽  
Intact Cells ◽  
E Coli ◽  
Low Concentrations ◽  
Transmembrane Pores ◽  
Diffusion Rates ◽  
Type Strains

Nutrients usually cross the outer membrane of Escherichia coli by diffusion through water-filled channels surrounded by a specific class of protein, porins. In this study, the rates of diffusion of hydrophilic nonelectrolytes, mostly sugars and sugar alcohols, through the porin channels were determined in two systems, (a) vesicles reconstituted from phospholipids and purified porin and (b) intact cells of mutant strains that produce many fewer porin molecules than wild-type strains. The diffusion rates were strongly affected by the size of the solute, even when the size was well within the "exclusion limit" of the channel. In both systems, hexoses and hexose disaccharides diffused through the channel at rates 50-80% and 2-4%, respectively, of that of a pentose, arabinose. Application of the Renkin equation to these data led to the estimate that the pore radius is approximately 0.6 nm, if the pore is assumed to be a hollow cylinder. The results of the study also show that the permeability of the outer membrane of the wild-type E. coli cell to glucose and lactose can be explained by the presence of porin channels, that a significant fraction of these channels must be functional or "open" under our conditions of growth, and that even 10(5) channels per cell could become limiting when E. coli tries to grow at a maximal rate on low concentrations of slowly penetrating solutes, such as disaccharides.

scholarly journals Phenothiazinium Antimicrobial Photosensitizers Are Substrates of Bacterial Multidrug Resistance Pumps

2006 ◽  
Vol 50 (1) ◽  
pp. 196-203 ◽  
Author(s):  
George P. Tegos ◽  
Michael R. Hamblin
Keyword(s):  
Escherichia Coli ◽  
Methylene Blue ◽  
Multidrug Resistance ◽  
Red Light ◽  
Antimicrobial Photodynamic Therapy ◽  
Wild Type ◽  
Microbial Cells ◽  
Chemical Structures ◽  
Wide Range ◽  
Type Strains

ABSTRACT Antimicrobial photodynamic therapy (PDT) combines a nontoxic photoactivatable dye, or photosensitizer (PS), with harmless visible light to generate singlet oxygen and free radicals that kill microbial cells. Although the light can be focused on the diseased area, the best selectivity is achieved by choosing a PS that binds and penetrates microbial cells. Cationic phenothiazinium dyes, such as methylene blue and toluidine blue O, have been studied for many years and are the only PSs used clinically for antimicrobial PDT. Multidrug resistance pumps (MDRs) are membrane-localized proteins that pump drugs out of cells and have been identified for a wide range of organisms. We asked whether phenothiazinium salts with structures that are amphipathic cations could potentially be substrates of MDRs. We used MDR-deficient mutants of Staphylococcus aureus (NorA), Escherichia coli (TolC), and Pseudomonas aeruginosa (MexAB) and found 2 to 4 logs more killing than seen with wild-type strains by use of three different phenothiazinium PSs and red light. Mutants that overexpress MDRs were protected from killing compared to the wild type. Effective antimicrobial PSs of different chemical structures showed no difference in light-mediated killing depending on MDR phenotype. Differences in uptake of phenothiazinium PS by the cells depending on level of MDR expression were found. We propose that specific MDR inhibitors could be used in combination with phenothiazinium salts to enhance their photodestructive efficiency.

scholarly journals Mutations That Activate the Silent bgl Operon of Escherichia coli Confer a Growth Advantage in Stationary Phase

2005 ◽  
Vol 187 (23) ◽  
pp. 7912-7917 ◽  
Author(s):  
Ranjna Madan ◽  
Roberto Kolter ◽  
S. Mahadevan
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Genetic System ◽  
Wild Type ◽  
Evolutionary Advantage ◽  
Type Strains

ABSTRACT Wild-type strains of Escherichia coli are unable to utilize aromatic β-glucosides such as arbutin and salicin because the major genetic system that encodes the functions for their catabolism, the bgl operon, is silent and uninducible. We show that strains that carry an activated bgl operon exhibit a growth advantage over the wild type in stationary phase in the presence of the rpoS819 allele that causes attenuated rpoS regulon expression. Our results indicate a possible evolutionary advantage in retaining the silent bgl operon by wild-type bacteria.

Involvement of outer membrane proteins in freeze–thaw resistance of Escherichia coli

1984 ◽  
Vol 30 (3) ◽  
pp. 339-344 ◽  
Author(s):  
Peter H. Calcott ◽  
Katherine N. Calcott
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Membrane Damage ◽  
Wild Type ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Porin Proteins ◽  
Protein Components ◽  
Type Strains

Two families of Escherichia coli mutants with altered outer membrane protein components were examined for sensitivity to freezing and thawing and other stresses. A mutant unable to make the lipoprotein (lpo) was extremely sensitive to freezing and thawing in water or saline and to challenge with detergent, while the mutant unable to make the porin proteins (ompB) was more resistant than the isogenic wild type; strains unable to make the tsx and ompA proteins were slightly more sensitive to the stresses. Similarly, the lpo deficient strain exhibited more and the ompB less wall and membrane damage than the wild-type strains. Little difference in the extent of wall damage, but more membrane damage, was seen for the two tsx and the ompA strains when compared with the wild-type strain. The roles of the specific proteins in determining sensitivity to freeze–thaw are discussed.

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