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J Foulds

Publications and source records attributed to J Foulds.

At least 55 records · Page 3Linked to original sources
PubMed1991

Regulation of ompF porin expression by salicylate in Escherichia coli.

The expression of ompF, the gene encoding a major outer membrane protein of Escherichia coli, is regulated by various environmental factors. The mechanism by which salicylate (SAL) drastically reduces ompF expression was studied here by means of lacZ fusions to ompF, ompC, and micF, by sodium dodecyl sulfate-gel electrophoresis of outer membrane proteins, and by measurements of outer membrane permeability. Growth of E. coli in LB broth containing SAL strongly reduced ompF-specific translation of an ompF-lacZ fusion. The extent of this reduction varied with the SAL concentration from 64% at 0.5 mM to 95% at 2 mM and greater than 99% at 10 mM. ompF-lacZ transcription was not affected by SAL, whereas ompC-lacZ transcription was elevated by 70%. Since the micF transcript is antisense to a portion of the ompF transcript and is capable of decreasing the translation of ompF, the effect of SAL on micF transcription was measured in a micF-lacZ fusion strain. SAL-grown cells contained three- to fourfold more micF transcript during the logarithmic phase of growth than did the control cultures. However, micF was not absolutely required for the response to SAL. In micF-deleted strains, the effects of SAL on ompF translation, on OmpF in the outer membrane, and on outer membrane permeability were diminished but still evident. The effect of SAL on ompF expression was independent of the osmolarity of the medium and was epistatic to certain ompB regulatory mutations: the high levels of ompF expression found in envZ3 and ompR472 strains were greatly reduced by growth in SAL. Unexpectedly, the OmpC- phenotypes of these mutants were suppressed by SAL. Thus, growth in SAL severely decreases the translation of ompF while enhancing the transcription of micF and ompC. In this respect, SAL-grown cells resemble certain marA and tolC mutants that have high levels of micF and ompC transcripts and low levels of OmpF.

Bacterial Outer Membrane Proteins↗
PubMed1990

The effects of muscle tension on cerebral circulation in blood-phobic and non-phobic subjects.

This study aimed to assess whether (1) a muscle tensing procedure which has been found to be useful in the treatment of blood-phobic patients produces an increase in heart rate and cerebral blood flow and (2) whether this increase is greater than that produced by mental effort alone. Subjects were 17 volunteers with a history of fainting in response to blood-injury stimuli, (12 were phobic) and 8 volunteers with no fainting history. They were required to (a) rest, (b) do mental arithmetic, and (c) repeatedly tense and release their arm and leg muscles. It was found that Ss, heart rate and cerebral blood flow velocity were significantly greater during the muscle tensing procedure than during mental arithmetic or resting conditions. The increased cerebral blood flow produced by muscle tensing may enable blood phobic patients to prevent fainting during exposure treatment.

Adolescent↗
PubMed1990

Heterogeneity of lipopolysaccharide phenotype among Salmonella typhi strains.

Comparison of the Vi antigen, lipopolysaccharide, and protein components of the cell surface of three strains of Salmonella typhi showed that differences in lipopolysaccharide contributed most to distinctions in serum survival, whereas differences in Vi antigen content had no apparent effect.

Antigens, Bacterial↗
PubMed1989

Decreased permeation of cephalosporins through the outer membrane of Escherichia coli grown in salicylates.

Escherichia coli K-12 cells grown in 1 to 5 mM sodium salicylate (SAL) or acetylsalicylate show increased phenotypic resistance to various antibiotics (J. L. Rosner, Proc. Natl. Acad. Sci. USA 82:8771-8774, 1985), including cephalosporins (this study). To determine whether these effects are caused by a decreased uptake of the antibiotics, the permeation of several cephalosporins through the outer membrane was measured. For E. coli K-12 grown in LB broth containing 5 mM SAL or acetylsalicylate, permeation of the outer membrane by the five cephalosporins tested decreased three- to fivefold compared with that in cells not grown in salicylates. Permeation of the outer membrane by cephaloridine decreased within 15 min of the addition of SAL to cells grown in broth and reached a minimum in 1 to 2 h. When cells were transferred from broth with SAL to broth without SAL, their permeability to cephaloridine increased slowly for the first 45 min and more rapidly over the next 1.5 h; the permeability then attained normal levels by 3 h. The permeability changes that occurred after media shifts, either to or from SAL, were prevented by concentrations of chloramphenicol that inhibited protein synthesis. These effects of SAL on outer membrane permeability are fully consistent with their effects on antibiotic resistance and with the report (T. Sawai, S. Hirano, and A. Yamaguchi, FEMS Microbiol. Lett. 40:233-237, 1987) that the outer membranes of SAL-treated cells are deficient in certain porins. Permeation of cephaloridine through the outer membrane also decreased when a virulent strain of E. coli K1 was grown in the presence of as little as 1 to 2 mM SAL. This raises the concern that high levels of salicylates in patients night interfere with cephalosporin or other antibiotic therapies.

Aspirin↗
PubMed1987

C3b generation is affected by the structure of the O-antigen polysaccharide in lipopolysaccharide from salmonellae.

Salmonellae differing in the O-antigen side chain of their lipopolysaccharide were previously shown to activate the alternative pathway of complement to different extents. We now examine the generation of the major cleavage fragment of the complement component C3 (C3b) on these bacteria in a system that contains the purified components C3, B, D, and P but lacks the regulatory proteins H and I. The deposition of C3b in this system reproduces the same pattern obtained earlier with the use of whole serum, with the expected differences among the strains bearing different O-antigen. However, two distinct mechanisms for these differences in C3b generation became apparent. The intermediate activating strain showed 3 to 4 times less initial deposition of C3b than the other two strains. In contrast, the least activating strain showed adequate initial deposition but poor amplification, as shown by 2 to 3.4 lower amplification indexes as compared with those on the other two strains. Binding studies with factor B showed that decreased C3 convertase formation was responsible for the low amplification on this strain. Only 25% of the C3b bound to its surface was able to bind factor B with a high affinity, in comparison with 90% on the other two strains. No differences were found for the binding of factor H among the strains. These studies identify the molecular mechanisms by which these bacteria avoid complement activation.

Antigens, Bacterial↗
PubMed1987

Multimeric C9 within C5b-9 is required for inner membrane damage to Escherichia coli J5 during complement killing.

We have shown recently that an average of three or more C9 molecules must bind to C5b-8 on Escherichia coli strain J5 to cause direct complement killing in the absence of serum lysozyme. We initially confirmed and extended this observation by showing that deposition of a large number of C5b-9 complexes bearing 1C9 per C5b-8 was not bactericidal for J5. To identify the target site for bactericidal C5b-9 deposition, we measured release of periplasmic and cytoplasmic markers of different size from J5 as the C9:C5b-8 ratio was changed, because the diameter of the C5b-9 channel is known to increase as the C9:C5b-8 ratio increases. To facilitate measurement of release of the periplasmic marker beta-lactamase (BLA), J5 was transformed for high level constitutive TEM-1 BLA production (J5-Amp). Multimeric C9 within C5b-9 (C9:C5b-8 greater than 3) was required to release BLA (m.w. 28,900) from J5-Amp regardless of whether cells bore 310, 560, or 890 C5b-9/organism. Curves of both BLA release and killing vs C9:C5b-8 ratio were sigmoidal and nearly superimposable. Release of the small cytoplasmic marker 86Rb, a potassium analog, also required a minimum C9:C5b-8 ratio of 3:1; specific 86Rb release did not occur in the absence of killing. Release of the large cytoplasmic marker beta-galactosidase (m.w. 505,000) did not occur even at the highest achievable C9:C5b-8 ratio of 11:1, despite greater than 99.9% killing, indicating that there was no dissolution of the peptidoglycan layer due to incomplete removal of serum lysozyme. Complement-mediated killing of J5 requires sufficient damage to the outer membrane or formation of a sufficiently large C5b-9 channel to release the large periplasmic marker BLA. The requirement of multimeric C9 for 86Rb release suggests that at low C9:C5b-8 ratios, either C5b-9 does not have access to the cytoplasmic space or that the J5 K+ transport systems are able to compensate for putative C5b-9 channels.

Blood Bactericidal Activity↗
PubMed1987

Lipopolysaccharide size and distribution determine serum resistance in Salmonella montevideo.

The survival of Salmonella montevideo during serum treatment depends on the presence of an O antigen (O-Ag) associated with the lipopolysaccharide molecule. In this organism, the O antigen is a polysaccharide composed of 0 to more than 55 subunits, each containing 4 mannose residues together with glucose and n-acetylglucosamine. We used a mutant strain of S. montevideo that requires exogenous mannose for the synthesis of O-Ag. Lipopolysaccharide (LPS) was prepared from these cells grown under three different conditions where the availability of exogenous mannose was regulated such that the average number of O-Ag units per LPS molecule, the percentage of LPS molecules bearing long O-Ag side chains, and the percentage of lipid A cores bearing O-Ag were all varied. These changes in LPS profiles were monitored on sodium dodecyl sulfate-polyacrylamide gels, and cells with different LPS profiles were tested for their ability to survive treatment with pooled normal human serum. Survival in serum was associated with LPS that contained an average of 4 to 5 O-Ag units per LPS molecule, and 20 to 23% of the LPS molecules had more than 14 O-Ag units per LPS molecule. Serum survival was less clearly associated with the percentage of lipid A cores covered with O-Ag. We propose, based on these data and on previous work, that the O-Ag polysaccharide provides the cell protection from serum killing by sterically hindering access of the C5b-9 complex to the outer membrane and that a critical density of long O-Ag polysaccharide is necessary to provide protection.

Antigens, Bacterial↗
PubMed1985

Cloning of extracellular DNase and construction of a DNase-negative strain of Vibrio cholerae.

The structural gene xds for extracellular DNase of Vibrio cholerae was cloned and inactivated by insertion of the transposon Tn5. The inactivated gene was introduced into the chromosome of V. cholerae by recombination to construct an extracellular DNase-negative strain. Tn5-mediated transposon-facilitated recombination was used to establish the position of xds between the pro-1 and ile-201 markers on the genetic map of V. cholerae. The extracellular DNase-negative strain described here should be useful for investigating the role of the xds-encoded DNase in the physiology of V. cholerae and its plasmids as well as for characterizing other DNases in this organism.

Cloning, Molecular↗
PubMed1983

Porin channels in Escherichia coli: studies with beta-lactams in intact cells.

Wild-type Escherichia coli K-12 produces two porins, OmpF (protein 1a) and OmpC (protein 1b). In mutants deficient in both of these "normal" porins, secondary mutants that produce a "new" porin, protein PhoE (protein E), are selected for. We determined the properties of the channels produced by each of these porins by measuring the rates of diffusion of various cephalosporins through the outer membrane in strains producing only one porin species. We found that all porin channels retarded the diffusion of more hydrophobic cephalosporins and that with monoanionic cephalosporins a 10-fold increase in the octanol-water partition coefficient of the solute produced a 5- to 6-fold decrease in the rate of penetration. Electrical charges of the solutes had different effects on different channels. Thus, with the normal porins (i.e., OmpF and OmpC proteins) additional negative charge drastically reduced the penetration rate through the channels, whereas additional positive charge significantly accelerated the penetration. In contrast, diffusion through the PhoE channel was unaffected by the presence of an additional negative charge. We hypothesize that the relative exclusion of hydrophobic and negatively charged solutes by normal porin channels is of ecological advantage to E. coli, which must exclude hydrophobic and anionic bile salts in its natural habitat. The properties of the PhoE porin are also consistent with the recent finding (M. Argast and W. Boos, J. Bacteriol. 143:142-150, 1980; J. Tommassen and B. Lugtenberg, J. Bacteriol. 143:151-157, 1980) that its biosynthesis is derepressed by phosphate starvation; the channel may thus act as an emergency pore primarily for the uptake of phosphate and phosphorylated compounds.

Bacterial Outer Membrane Proteins↗
PubMed1983

Escherichia coli outer membrane protein K is a porin.

Protein K is an outer membrane protein found in pathogenic encapsulated strains of Escherichia coli. We present evidence here that protein K is structurally and functionally related to the E. coli K-12 porin proteins (OmpF, OmpC, and PhoE). Protein K was found to cross-react with antibody to OmpF protein and to share 8 out of 17 peptides in common with the OmpF protein. Strains that are OmpC porin- and OmpF porin- and contain protein K as their major outer membrane protein have increased rates of uptake of nutrients and a faster growth rate relative to the parental porin- strain. The protein K-containing strains are at least 1,000-fold more sensitive to colicins E2 and E3 than is the porin -deficient strain. These data suggest that protein K is a functional porin in E. coli. The porin function of protein K was also demonstrated in vitro, using black lipid membranes. Protein K increased the conductance in these membranes in discrete, uniform steps characteristic of channels with a size of about 2 nS.

Bacterial Outer Membrane Proteins↗
PubMed1982

Colicin A receptor: role of two Escherichia coli outer membrane proteins (OmpF protein and btuB gene product) and lipopolysaccharide.

ompF cells were completely resistant to colicin A, whereas btuB cells were partially resistant. The OmpF protein, in the presence of added lipopolysaccharide, inactivated colicin A. This inactivation was enhanced by added btuB gene product, btuB gene product with lipopolysaccharide did not inactivate colicin A. These data, together with the observation that vitamin B12 protected btuB+ cells from the killing effect of colicin A, suggest that the colicin A receptor in Escherichia coli K-12 is composed of the OmpF protein, the btuB gene product, and lipopolysaccharide.

Adsorption↗
PubMed1979

Inactivation of bacteriophages by protein E, a new major membrane protein isolated from an Escherichia coli mutant.

Pure protein E, obtained after diethylaminoethyl-cellulose chromatography of ethylenediaminetetraacetic acid-Triton X-100-solubilized outer membrane proteins of Escherichia coli strain JF694, inactivated bacteriophage K3. Lipopolysaccharide enhanced bacteriophage inactivation. Antibody prepared against purified protein E protected bacteriophage K3 from inactivation by protein E. Bacteriophage K3 used a major outer membrane protein, protein II*, as part of its receptor. We conclude that proteins E and II* have a common region which interacts with bacteriophage K3. Protein E also inactivated two recently described bacteriophages, TC45 and TC23, that use protein E as at least part of their receptor.

Antigens, Viral↗
PubMed1979

Isolation and partial characterization of protein E, a major protein found in certain Escherichia coli K-12 mutant strains: relationship to other outer membrane proteins.

Escherichia coli outer membrane protein E was purified, and its amino acid composition and N-terminal amino acid were determined. The purified protein was shown to be immunologically and electrophoretically identical to proteins Ic (U. Henning, W. Schmidmayr, and I. Hindennach, Mol. Gen. Genet. 154:293-298, 1977) and e (W. van Alphen, N. van Selm, and B. Lugtenberg, Mol. Gen. Genet. 159:75-83, 1978). Proteins E, e, and Ic were also immunologically related to E. coli outer membrane protein Ia. Lugtenberg and co-workers (B. Lugtenberg, R. van Boxtel, C. Verhoef, and W. van Alphen, FEBS Lett. 96:99-105, 1978) have shown that electrophoretically identical peptides were generated by cyanogen bromide treatment of proteins E, e, and Ic.

Amino Acids↗
PubMed1978

Defeat of colicin tolerance in Escherichia coli ompA mutants: evidence for interaction between colicin L-JF246 and the cytoplasmic membrane.

Escherichia coli ompA mutants are tolerant to colicin L-JF246. This tolerance can be overcome by a variety of treatments that have as their target the outer membrane or the peptidoglycan layers of the cell envelope. Thus, increasing the concentration of colicin L, releasing lipopolysaccharide from the outer membrane by treatment of intact cells with ethylenediaminetetracetic acid (EDTA), converting cells to spheroplasts by treatment with lysozyme-EDTA or penicillin, or trypsin, treatment of intact cells will result in an increased colicin sensitivity. These treatments alter the outer membrane of ompA mutants and suggest that the altered outer membrane may allow the penetration of at least a portion of the colicin L molecule to a site of action located within this barrier. To substantiate this, we have demonstrated that membrane vesicles prepared from ompA mutants are sensitive to colicin L and that 14C-labeled colicin L binds rapidly to both the outer and inner membrane fractions of the cell.

Cell Fractionation↗
PubMed1978

New major outer membrane proteins found in an Escherichia coli tolF mutant resistant to bacteriophage TuIb.

Cell envelopes prepared from an Escherichia coli tolF strain selected as resistant to phage TuIb contained a new major outer membrane protein related to outer membrane proteins Ia and Ib. The strain that produces this protein is a tolF par double mutant but contains an additional mutation leading to the production of the new major outer membrane protein. Antibiotic sensitivity lost as a result of the tolF mutation is regained in strains that contain the new major outer membrane protein. This indicates that this protein functions to restore the selective permeability of the outer membrane to low-molecular-weight hydrophilic molecules.

Anti-Bacterial Agents↗
PubMed1978

Two bacteriophages which utilize a new Escherichia coli major outer membrane protein as part of their receptor.

Escherichia coli strain JF694 contains a new major outer membrane protein which we have called protein E (J. Foulds, and T. Chai, J. Bacteriol. 133:1478-1483). Two new bacteriophages, TC45 and TC23, were isolated that require the presence of protein E in the outer membrane of host cells for growth. Both of these bacteriophages have a morphology similar to T-even bacteriophages but are distinct in properties such as plaque morphology, buoyant density, and burst size. Although strain JF694, containing protein E, adsorbs bacteriophage TC45 efficiently, cells killed with heat or chloroform are unable to inactivate this bacteriophage. Purified protein E either in the presence or absence of additional probable cofactors such as lipopolysaccharide was also unable to inactivate bacteriophage TC45. Both bacteriophages probably use protein E as at least part of their receptor but require, in addition, other outer membrane components or a specific orientation or organization of this protein in the outer membrane.

Adsorption↗