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 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.

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.

Biofilm Growth of Escherichia coli Is Subject to cAMP-Dependent and cAMP-Independent Inhibition

2015 ◽  
Vol 25 (2-3) ◽  
pp. 209-225 ◽  
Author(s):  
Sarah L. Sutrina ◽  
Kia Daniel ◽  
Michael Lewis ◽  
Naomi T. Charles ◽  
Cherysa K.E. Anselm ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Catabolite Repression ◽  
Ph Effects ◽  
Wild Type ◽  
Inhibitory Effects ◽  
Phosphotransferase System ◽  
Biofilm Growth ◽  
E Coli ◽  
Low Concentrations ◽  
High Concentrations

We established that <i>Escherichia coli </i>strain 15 (ATCC 9723) produces both curli and cellulose, and forms robust biofilms. Since this strain is wild type with respect to the phosphoenolpyruvate:sugar phosphotransferase system (PTS), it is an ideal strain in which to investigate the effects of the PTS on the biofilm growth of <i>E. coli</i>. We began by looking into the effects of PTS and non-PTS sugars on the biofilm growth of this strain. All the sugars tested tended to activate biofilm growth at low concentrations but to inhibit biofilm growth at high concentrations. Acidification of the medium was an inhibitory factor in the absence of buffer, but buffering to prevent a pH drop did not prevent the inhibitory effects of the sugars. The concentration at which inhibition set in varied from sugar to sugar. For most sugars, cyclic (c)AMP counteracted the inhibition at the lowest inhibitory concentrations but became ineffective at higher concentrations. Our results suggest that cAMP-dependent catabolite repression, which is mediated by the PTS in <i>E. coli</i>, plays a role in the regulation of biofilm growth in response to sugars. cAMP-independent processes, possibly including Cra, also appear to be involved, in addition to pH effects.

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.

scholarly journals Cloning of the chromosomal determinants encoding hemolysin production and mannose-resistant hemagglutination in Escherichia coli

1982 ◽  
Vol 152 (3) ◽  
pp. 1241-1247
Author(s):  
H Berger ◽  
J Hacker ◽  
A Juarez ◽  
C Hughes ◽  
W Goebel
Keyword(s):  
Escherichia Coli ◽  
High Frequency ◽  
Wild Type ◽  
Chromosomal Dna ◽  
Genetic Determinants ◽  
E Coli ◽  
Gene Banks ◽  
In The Wild ◽  
K 12 ◽  
Type Strains

We have cloned the chromosomal hemolysin determinants from Escherichia coli strains belonging to the four O-serotypes O4, O6, O18, and O75. The hemolysin-producing clones were isolated from gene banks of these strains which were constructed by inserting partial Sau3A fragments of chromosomal DNA into the cosmid pJC74. The hemolytic cosmid clones were relatively stable. The inserts were further subcloned either as SalI fragments in pACYC184 or as BamHI-SalI fragments in a recombinant plasmid (pANN202) containing cistron C (hlyC) of the plasmid-encoded hemolysin determinant. Detailed restriction maps of each of these determinants were constructed, and it was found that, despite sharing overall homology, the determinants exhibited minor specific differences in their structure. These appeared to be restricted to cistron A (hlyA), which is the structural gene for hemolysin. In the gene banks of two of these hemolytic strains, we could also identify clones which carried the genetic determinants for the mannose-resistant hemagglutination antigens Vb and VIc. Both of these fimbrial antigens were expressed in the E. coli K-12 clones to an extent similar to that observed in the wild-type strains. These recombinant cosmids were rather unstable, and, in the absence of selection, segregated at a high frequency.

scholarly journals The Escherichia coli Efflux Pump TolC Promotes Aggregation of Enteroaggregative E. coli 042

2007 ◽  
Vol 76 (3) ◽  
pp. 1247-1256 ◽  
Author(s):  
Naoko Imuta ◽  
Junichiro Nishi ◽  
Koichi Tokuda ◽  
Rika Fujiyama ◽  
Kunihiro Manago ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Efflux Pump ◽  
Microtiter Plate ◽  
Virulence Plasmid ◽  
Wild Type ◽  
Planktonic Cells ◽  
Microtiter Plate Assay ◽  
E Coli ◽  
Aggregative Adherence

ABSTRACT Enteroaggregative Escherichia coli (EAEC) is an emerging enteric pathogen in both developing and industrialized countries. EAEC is defined as a diarrheal pathogen based on its characteristic aggregative adherence to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa. We have reported that the novel protein AatA, which is encoded on the EAEC virulence plasmid pAA2, localizes to the outer membrane and facilitates export of the dispersin Aap across the outer membrane. Because AatA is an E. coli efflux pump TolC homolog, we investigated the role of TolC in the virulence of EAEC. No difference in Aap secretion was observed between the wild type and its tolC mutant (042tolC). However, characteristic aggregation in high-glucose Dulbecco's minimal essential medium for the wild type was diminished for 042tolC. In a microtiter plate assay, there were significantly more planktonic cells for 042tolC than for the wild type, while there were significantly fewer spontaneously precipitated cells on the substratum for 042tolC than for the wild type. In a HEp-2 cell adherence test, 042tolC showed less aggregative adherence than did the wild type. The strong aggregation and aggregative adherence were restored in the complement strain with tolC. In a transwell assay, planktonic cells of 042tolC decreased when cocultured with the wild type or the complement, while precipitated cells of 042tolC increased when cocultured with them. These results suggest that TolC promotes the aggregation and adhesion of EAEC 042 by secreting an assumed humoral factor.

scholarly journals The β-Oxidation Systems of Escherichia coli and Salmonella enterica Are Not Functionally Equivalent

2006 ◽  
Vol 188 (2) ◽  
pp. 599-608 ◽  
Author(s):  
Surtaj Hussain Iram ◽  
John E. Cronan
Keyword(s):  
Escherichia Coli ◽  
Oleic Acid ◽  
Fatty Acid ◽  
Octanoic Acid ◽  
Decanoic Acid ◽  
Wild Type ◽  
Fatty Acid Degradation ◽  
E Coli ◽  
Acid Degradation ◽  
Type Strains

ABSTRACT Based on its genome sequence, the pathway of β-oxidative fatty acid degradation in Salmonella enterica serovar Typhimurium LT2 has been thought to be identical to the well-characterized Escherichia coli K-12 system. We report that wild-type strains of S. enterica grow on decanoic acid, whereas wild-type E. coli strains cannot. Mutant strains (carrying fadR) of both organisms in which the genes of fatty acid degradation (fad) are expressed constitutively are readily isolated. The S. enterica fadR strains grow more rapidly than the wild-type strains on decanoic acid and also grow well on octanoic and hexanoic acids (which do not support growth of wild-type strains). By contrast, E. coli fadR strains grow well on decanoic acid but grow only exceedingly slowly on octanoic acid and fail to grow at all on hexanoic acid. The two wild-type organisms also differed in the ability to grow on oleic acid when FadR was overexpressed. Under these superrepression conditions, E. coli failed to grow, whereas S. enterica grew well. Exchange of the wild-type fadR genes between the two organisms showed this to be a property of S. enterica rather than of the FadR proteins per se. This difference in growth was attributed to S. enterica having higher cytosolic levels of the inducing ligands, long-chain acyl coenzyme As (acyl-CoAs). The most striking results were the differences in the compositions of CoA metabolites of strains grown with octanoic acid or oleic acid. S. enterica cleanly converted all of the acid to acetyl-CoA, whereas E. coli accumulated high levels of intermediate-chain-length products. Exchange of homologous genes between the two organisms showed that the S. enterica FadE and FadBA enzymes were responsible for the greater efficiency of β-oxidation relative to that of E. coli.

Sensitivity of Escherichia coli to Viral Nucleic Acid, XII. Ca2+-or Ba2+-Facilitated Transfection of Cell Envelope Mutants

1977 ◽  
Vol 32 (5-6) ◽  
pp. 429-433 ◽  
Author(s):  
Akira Taketo
Keyword(s):  
Escherichia Coli ◽  
Nucleic Acid ◽  
Outer Membrane ◽  
Cell Envelope ◽  
Nucleoside Transport ◽  
Wild Type ◽  
Viral Nucleic Acid ◽  
E Coli ◽  
The Relationship ◽  
Cellular Competence

Abstract Using various envelope mutants of Escherichia coli, the relationship between cell surface struc­ture and the Ca2+-or Ba2+-dependent competence for transfection was investigated. In contrast with rough strains, smooth bacteria treated with Ca2+ or Ba2+ were incompetent for the trans­fection by ØA RF. In E. coli K12 D21 derivatives, Ca2+-dependent competence remarkably in­ creased by lpsAl mutation and the highest level of competence was attained by further deficiency in glucose units of the LPS. Upon treatment with BaCl2 , strain D21 and its lpsAl mutant became highly competent for ØA RF. The effect of Ba2+ was, however, feeble for lpsAl mutants further deficient in heptose units and/or glucose units. Among different LPS mutants of E. coli B, variation of the Ca2+-or Ba2+-dependent competence was relatively small and even the competence of strain BB12, whose LPS core contained only two KDO units, was nearly equal to that of wild type bacteria. However, the level of cellular competence induced by Ba2+ was not allways parallel to that induced by Ca2+. In mutants deficient in outer membrane protein I, either Ca2+-or Ba2+-dependent competence increased several-fold, whereas in mutants devoid of outer membrane II*, the com­petence decreased considerably. Unlike nucleoside transport, the uptake of DNA was not affected by tsx mutation.

scholarly journals Diversity of Hemagglutination Phenotypes among P-Fimbriated Wild-Type Strains of Escherichia coli in Relation to papG Allele Repertoire

1998 ◽  
Vol 5 (2) ◽  
pp. 160-170 ◽  
Author(s):  
James R. Johnson ◽  
Jennifer J. Brown ◽  
Parvia Ahmed
Keyword(s):  
Escherichia Coli ◽  
Phenotypic Diversity ◽  
Class Ii ◽  
Class I ◽  
Class Iii ◽  
Wild Type ◽  
Sheep Erythrocytes ◽  
E Coli ◽  
Naturally Occurring ◽  
Type Strains

ABSTRACT Data regarding the hemagglutination (HA) patterns of the three variants (classes I, II, and III) of the Escherichia coliadhesin PapG are conflicting. These HA patterns usually have been assessed for each papG allele separately with recombinant strains in slide HA assays. We rigorously evaluated an alternative microtiter tray HA assay and then used it to assess the HA of four erythrocyte types (human A1P1 and OP1, rabbit, and sheep erythrocytes) by multiple wild-typeE. coli strains representing the four naturally occurring combinations of the papG alleles, i.e., class I plus III, class III only, class II plus III, and class II only. The microtiter tray HA assay displayed significantly better reproducibility of intraobserver (83%) and interobserver (86%) results than did slide HA assays (39 and 73%, respectively). Novel findings from the study of 32 wild-type P-fimbriated strains included reproducible determinations of phenotypic diversity among different papG categories, among strains within each papG category, and from day to day for individual strains. There was also substantial overlap of phenotypes between papG categories I plus III and III only and between II plus III and II only. A class III papG recombinant strain’s HA pattern differed significantly from that of the wild-type class III strains. These data demonstrate that HA phenotypes of wild-type P-fimbriated E. coli strains can be reproducibly assessed by a microtiter HA assay and that they correspond broadly topapG genotype but in a more complex and varied fashion than previously recognized.

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