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  • De Spiegeleer, Philipp  (5)
  • 1
    Online Resource
    Online Resource
    Role of Porins in Sensitivity of Escherichia coli to Antibacterial Activity of the Lactoperoxidase Enzyme System
    American Society for Microbiology ; 2005
    In:  Applied and Environmental Microbiology Vol. 71, No. 7 ( 2005-07), p. 3512-3518
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 71, No. 7 ( 2005-07), p. 3512-3518
    Abstract: Lactoperoxidase is an enzyme that contributes to the antimicrobial defense in secretory fluids and that has attracted interest as a potential biopreservative for foods and other perishable products. Its antimicrobial activity is based on the formation of hypothiocyanate (OSCN − ) from thiocyanate (SCN − ), using H 2 O 2 as an oxidant. To gain insight into the antibacterial mode of action of the lactoperoxidase enzyme system, we generated random transposon insertion mutations in Escherichia coli MG1655 and screened the resultant mutants for an altered tolerance of bacteriostatic concentrations of this enzyme system. Out of the ca. 5,000 mutants screened, 4 showed significantly increased tolerance, and 2 of these had an insertion, one in the waaQ gene and one in the waaO gene, whose products are involved in the synthesis of the core oligosaccharide moiety of lipopolysaccharides. Besides producing truncated lipopolysaccharides and displaying hypersensitivity to novobiocin and sodium dodecyl sulfate (SDS), these mutants were also shown by urea-SDS-polyacrylamide gel electrophoresis analysis to have reduced amounts of porins in their outer membranes. Moreover, they showed a reduced degradation of p -nitrophenyl phosphate and an increased resistance to ampicillin, two indications of a decrease in outer membrane permeability for small hydrophilic solutes. Additionally, ompC and ompF knockout mutants displayed levels of tolerance to the lactoperoxidase system similar to those displayed by the waa mutants. These results suggest that mutations which reduce the porin-mediated outer membrane permeability for small hydrophilic molecules lead to increased tolerance to the lactoperoxidase enzyme system because of a reduced uptake of OSCN − .
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.71.7.3512-3518.2005
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    CorA Affects Tolerance of Escherichia coli and Salmonella enterica Serovar Typhimurium to the Lactoperoxidase Enzyme System but Not to Other Forms of Oxidative Stress
    American Society for Microbiology ; 2005
    In:  Applied and Environmental Microbiology Vol. 71, No. 11 ( 2005-11), p. 6515-6523
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 71, No. 11 ( 2005-11), p. 6515-6523
    Abstract: The enzyme lactoperoxidase is part of the innate immune system in vertebrates and owes its antimicrobial activity to the formation of oxidative reaction products from various substrates. In a previous study, we have reported that, with thiocyanate as a substrate, the lactoperoxidase system elicits a distinct stress response in Escherichia coli MG1655. This response is different from but partly overlapping with the stress responses to hydrogen peroxide and to superoxide. In the current work, we constructed knockouts in 10 lactoperoxidase system-inducible genes to investigate their role in the tolerance of E. coli MG1655 to this antimicrobial system. Five mutations resulted in a slightly increased sensitivity, but one mutation ( corA ) caused hypersensitivity to the lactoperoxidase system. This hypersensitive phenotype was specific to the lactoperoxidase system, since neither the sensitivity to hydrogen peroxide nor to the superoxide generator plumbagin was affected in the corA mutant. Salmonella enterica serovar Typhimurium corA had a similar phenotype. Although corA encodes an Mg 2+ transporter and at least three other inducible open reading frames belonged to the Mg 2+ regulon, repression of the Mg stimulon by Mg 2+ did not change the lactoperoxidase sensitivity of either the wild-type or corA mutant. Prior exposure to 0.3 mM Ni 2+ , which is also transported by CorA, strongly sensitized MG1655 but not the corA mutant to the lactoperoxidase system. Furthermore, this Ni 2+ -dependent sensitization was suppressed by the CorA-specific inhibitor Co(III) hexaammine. These results indicate that CorA affects the lactoperoxidase sensitivity of E. coli by modulating the cytoplasmic concentrations of transition metals that enhance the toxicity of the lactoperoxidase system.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.71.11.6515-6523.2005
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Unique stress response to the lactoperoxidase-thiocyanate enzyme system in Escherichia coli
    Elsevier BV ; 2005
    In:  Research in Microbiology Vol. 156, No. 2 ( 2005-03), p. 225-232
    Details
    In: Research in Microbiology, Elsevier BV, Vol. 156, No. 2 ( 2005-03), p. 225-232
    Type of Medium: Online Resource
    ISSN: 0923-2508
    URL: Article
    DOI: 10.1016/j.resmic.2004.09.012
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2005
    detail.hit.zdb_id: 2010710-9
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Heat Shock Protein-Mediated Resistance to High Hydrostatic Pressure in Escherichia coli
    American Society for Microbiology ; 2004
    In:  Applied and Environmental Microbiology Vol. 70, No. 5 ( 2004-05), p. 2660-2666
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 70, No. 5 ( 2004-05), p. 2660-2666
    Abstract: A random library of Escherichia coli MG1655 genomic fragments fused to a promoterless green fluorescent protein (GFP) gene was constructed and screened by differential fluorescence induction for promoters that are induced after exposure to a sublethal high hydrostatic pressure stress. This screening yielded three promoters of genes belonging to the heat shock regulon ( dnaK , lon , clpPX ), suggesting a role for heat shock proteins in protection against, and/or repair of, damage caused by high pressure. Several further observations provide additional support for this hypothesis: (i) the expression of rpoH , encoding the heat shock-specific sigma factor σ 32 , was also induced by high pressure; (ii) heat shock rendered E. coli significantly more resistant to subsequent high-pressure inactivation, and this heat shock-induced pressure resistance followed the same time course as the induction of heat shock genes; (iii) basal expression levels of GFP from heat shock promoters, and expression of several heat shock proteins as determined by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins extracted from pulse-labeled cells, was increased in three previously isolated pressure-resistant mutants of E. coli compared to wild-type levels.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.70.5.2660-2666.2004
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    Induction of Oxidative Stress by High Hydrostatic Pressure in Escherichia coli
    American Society for Microbiology ; 2005
    In:  Applied and Environmental Microbiology Vol. 71, No. 5 ( 2005-05), p. 2226-2231
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 71, No. 5 ( 2005-05), p. 2226-2231
    Abstract: Using leaderless alkaline phosphatase as a probe, it was demonstrated that pressure treatment induces endogenous intracellular oxidative stress in Escherichia coli MG1655. In stationary-phase cells, this oxidative stress increased with the applied pressure at least up to 400 MPa, which is well beyond the pressure at which the cells started to become inactivated (200 MPa). In exponential-phase cells, in contrast, oxidative stress increased with pressure treatment up to 150 MPa and then decreased again, together with the cell counts. Anaerobic incubation after pressure treatment significantly supported the recovery of MG1655, while mutants with increased intrinsic sensitivity toward oxidative stress ( katE , katF , oxyR , sodAB , and soxS ) were found to be more pressure sensitive than wild-type MG1655. Furthermore, mild pressure treatment strongly sensitized E. coli toward t- butylhydroperoxide and the superoxide generator plumbagin. Finally, previously described pressure-resistant mutants of E. coli MG1655 displayed enhanced resistance toward plumbagin. In one of these mutants, the induction of endogenous oxidative stress upon high hydrostatic pressure treatment was also investigated and found to be much lower than in MG1655. These results suggest that, at least under some conditions, the inactivation of E. coli by high hydrostatic pressure treatment is the consequence of a suicide mechanism involving the induction of an endogenous oxidative burst.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.71.5.2226-2231.2005
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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