GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    One-pot exfoliation and surface functionalization of MoS2: A potential nanofiller to overcome the brittleness of polystyrene (PS)
    Elsevier BV ; 2021
    In:  Polymer Vol. 233 ( 2021-10), p. 124187-
    Details
    In: Polymer, Elsevier BV, Vol. 233 ( 2021-10), p. 124187-
    Type of Medium: Online Resource
    ISSN: 0032-3861
    URL: Article
    DOI: 10.1016/j.polymer.2021.124187
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 2013972-X
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Characterization of the oxidative stress response regulatory network in Bacteroides fragilis: An interaction between BmoR and OxyR regulons promotes abscess formation in a model of intra-abdominal infection
    Elsevier BV ; 2022
    In:  Anaerobe Vol. 78 ( 2022-12), p. 102668-
    Details
    In: Anaerobe, Elsevier BV, Vol. 78 ( 2022-12), p. 102668-
    Type of Medium: Online Resource
    ISSN: 1075-9964
    URL: Article
    DOI: 10.1016/j.anaerobe.2022.102668
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2022
    detail.hit.zdb_id: 1461095-4
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Deletion of BmoR affects the expression of genes related to thiol/disulfide balance in Bacteroides fragilis
    Springer Science and Business Media LLC ; 2018
    In:  Scientific Reports Vol. 8, No. 1 ( 2018-09-26)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 8, No. 1 ( 2018-09-26)
    Abstract: Bacteroides fragilis , an opportunistic pathogen and commensal bacterium in the gut, is one the most aerotolerant species among strict anaerobes. However, the mechanisms that control gene regulation in response to oxidative stress are not completely understood. In this study, we show that the MarR type regulator, BmoR, regulates the expression of genes involved in the homeostasis of intracellular redox state. Transcriptome analysis showed that absence of BmoR leads to altered expression in total of 167 genes. Sixteen of these genes had a 2-fold or greater change in their expression. Most of these genes are related to LPS biosynthesis and carbohydrates metabolism, but there was a significant increase in the expression of genes related to the redox balance inside the cell. A pyridine nucleotide-disulfide oxidoreductase located directly upstream of bmoR was shown to be repressed by direct binding of BmoR to the promoter region. The expression of two other genes, coding for a thiosulphate:quinone-oxidoreductase and a thioredoxin, are indirectly affected by bmoR mutation during oxygen exposure. Phenotypic assays showed that BmoR is important to maintain the thiol/disulfide balance in the cell, confirming its relevance to B . fragilis response to oxidative stress.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-018-32880-7
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 2615211-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Transcriptional regulation of the Bacteroides fragilis ferritin gene (ftnA) by redox stress
    Microbiology Society ; 2004
    In:  Microbiology Vol. 150, No. 7 ( 2004-07-01), p. 2125-2134
    Details
    In: Microbiology, Microbiology Society, Vol. 150, No. 7 ( 2004-07-01), p. 2125-2134
    Type of Medium: Online Resource
    ISSN: 1350-0872 , 1465-2080
    URL: Article
    DOI: 10.1099/mic.0.26948-0
    Language: English
    Publisher: Microbiology Society
    Publication Date: 2004
    detail.hit.zdb_id: 2008736-6
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    The uroS and yifB Genes Conserved among Tetrapyrrole Synthesizing-Deficient Bacteroidales Are Involved in Bacteroides fragilis Heme Assimilation and Survival in Experimental Intra-abdominal Infection and Intestinal Colonization
    American Society for Microbiology ; 2020
    In:  Infection and Immunity Vol. 88, No. 8 ( 2020-07-21)
    Details
    In: Infection and Immunity, American Society for Microbiology, Vol. 88, No. 8 ( 2020-07-21)
    Abstract: The human intestinal anaerobic commensal and opportunistic pathogen Bacteroides fragilis does not synthesize the tetrapyrrole protoporphyrin IX in order to form heme that is required for growth stimulation and survival in vivo . Consequently, B. fragilis acquires essential heme from host tissues during extraintestinal infection. The absence of several genes necessary for de novo heme biosynthesis is a common characteristic of many anaerobic bacteria; however, the uroS gene, encoding a uroporphyrinogen III synthase for an early step of heme biosynthesis, is conserved among the heme-requiring Bacteroidales that inhabit the mammalian gastrointestinal tract. In this study, we show that the ability of B. fragilis to utilize heme or protoporphyrin IX for growth was greatly reduced in a Δ uroS mutant. This growth defect appears to be linked to the suppression of reverse chelatase and ferrochelatase activities in the absence of uroS . In addition, this Δ uroS suppressive effect was enhanced by the deletion of the yifB gene, which encodes an Mg 2+ -chelatase protein belonging to the A TPases a ssociated with various cellular a ctivities (AAA + ) superfamily of proteins. Furthermore, the Δ uroS mutant and the Δ uroS Δ yifB double mutant had a severe survival defect compared to the parent strain in competitive infection assays using animal models of intra-abdominal infection and intestinal colonization. This shows that the presence of the uroS and yifB genes in B. fragilis seems to be linked to pathophysiological and nutritional competitive fitness for survival in host tissues. Genetic complementation studies and enzyme kinetics assays indicate that B. fragilis UroS is functionally different from canonical bacterial UroS proteins. Taken together, these findings show that heme assimilation and metabolism in the anaerobe B. fragilis have diverged from those of aerobic and facultative anaerobic pathogenic bacteria.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    URL: Article
    DOI: 10.1128/IAI.00103-20
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2020
    detail.hit.zdb_id: 1483247-1
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    Aerobic-Type Ribonucleotide Reductase in the Anaerobe Bacteroides fragilis
    American Society for Microbiology ; 2002
    In:  Journal of Bacteriology Vol. 184, No. 4 ( 2002-02-15), p. 895-903
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 184, No. 4 ( 2002-02-15), p. 895-903
    Abstract: Bacteroides fragilis , a component of the normal intestinal flora, is an obligate anaerobe capable of long-term survival in the presence of air. Survival is attributed to an elaborate oxidative stress response that controls the induction of more than 28 peptides, but there is limited knowledge concerning the identities of these peptides. In this report, RNA fingerprinting by arbitrarily primed PCR identified five new genes whose expression increased following exposure to O 2 . Nucleotide sequence analysis of the cloned genes indicated that they encoded an outer membrane protein, an aspartate decarboxylase, an efflux pump, heat shock protein HtpG, and an NrdA ortholog constituting the large subunit of a class Ia ribonucleotide reductase (RRase). Attention was focused on the nrdA gene since class I RRases are obligate aerobic enzymes catalyzing the reduction of ribonucleoside 5′-diphosphates by a mechanism that requires molecular oxygen for activity. Sequence analysis of the nrd locus showed that two genes, nrdA and nrdB , are located in the same orientation in a 4.5-kb region. Northern hybridization and primer extension experiments confirmed induction of the genes by O 2 and suggested they are an operon. The B. fragilis nrdA and nrdB genes were overexpressed in Escherichia coli , and CDP reductase assays confirmed that they encoded an active enzyme. The enzyme activity was inhibited by hydroxyurea, and ATP was shown to be a positive effector of CDP reductase activity, while dATP was an inhibitor, indicating that the enzyme was a class Ia RRase. A nrdA mutant was viable under anaerobic conditions but had decreased survival following exposure to O 2 , and it could not rapidly resume growth after O 2 treatment. The results presented indicate that during aerobic conditions B. fragilis NrdAB may have a role in maintaining deoxyribonucleotide pools for DNA repair and growth recovery.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/jb.184.4.895-903.2002
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2002
    detail.hit.zdb_id: 1481988-0
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 7
    Online Resource
    Online Resource
    Thioredoxin Reductase Is Essential for Thiol/Disulfide Redox Control and Oxidative Stress Survival of the Anaerobe Bacteroides fragilis
    American Society for Microbiology ; 2007
    In:  Journal of Bacteriology Vol. 189, No. 22 ( 2007-11-15), p. 8015-8023
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 189, No. 22 ( 2007-11-15), p. 8015-8023
    Abstract: Results of this study showed that the anaerobic, opportunistic pathogen Bacteroides fragilis lacks the glutathione/glutaredoxin redox system and possesses an extensive number of putative thioredoxin (Trx) orthologs. Analysis of the genome sequence revealed six Trx orthologs and an absence of genes required for synthesis of glutathione and glutaredoxins. In addition, it was shown that the thioredoxin reductase (TrxB)/Trx system is the major or sole redox system for thiol/disulfide cellular homeostasis in this anaerobic bacterium. Expression of the B. fragilis trxB gene was induced following treatment with diamide or H 2 O 2 or exposure to oxygen. This inducible trxB expression was OxyR independent. Northern blot hybridization analysis showed that the trxB mRNA was cotranscribed with lolA as a bicistronic transcript or was present as a monocistronic transcript that was also highly induced under the same conditions. The role of LolA, a prokaryotic periplasmic lipoprotein-specific molecular chaperone in the thiol/disulfide redox system, is unknown. A trxB deletion mutant was more sensitive to the effects of diamide and oxygen than the parent strain. In addition, the trxB mutant was unable to grow in culture media without addition of a reductant. Furthermore, the trxB mutant was not able to induce intraabdominal abscess formation in a mouse model, whereas the parent strain was. Taken together, these data strongly suggest that TrxB/Trx is the major, if not the sole, thiol/disulfide redox system in this anaerobe required for survival and abscess formation in a peritoneal cavity infection model.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.00714-07
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 1481988-0
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 8
    Online Resource
    Online Resource
    Role of the Alkyl Hydroperoxide Reductase ( ahpCF ) Gene in Oxidative Stress Defense of the Obligate Anaerobe Bacteroides fragilis
    American Society for Microbiology ; 1999
    In:  Journal of Bacteriology Vol. 181, No. 18 ( 1999-09-15), p. 5701-5710
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 181, No. 18 ( 1999-09-15), p. 5701-5710
    Abstract: In this study we report the identification and role of the alkyl hydroperoxide reductase ( ahp ) gene in Bacteroides fragilis . The two components of ahp , ahpC , and ahpF , are organized in an operon, and the deduced amino acid sequences revealed that B. fragilis AhpCF shares approximately 60% identity to orthologues in other gram-positive and gram-negative bacteria. Northern blot hybridization analysis of total RNA showed that the ahpCF genes were transcribed as a polycistronic 2.4-kb mRNA and that ahpC also was present as a 0.6-kb monocistronic mRNA. ahpC and ahpCF mRNAs were induced approximately 60-fold following H 2 O 2 treatment or oxygen exposure of the parent strain but were constitutive in a peroxide-resistant strain. Further investigation using an ahpCF ′::β-xylosidase gene transcriptional fusion confirmed that ahpCF had lost normal regulation in the peroxide-resistant strain compared to the parent. The ahpCF mutant was more sensitive to growth inhibition and mutagenesis by organic peroxides than the parent strain, as determined by disk inhibition assays and the frequency of mutation to fusidic acid resistance. This finding suggests that the ahp genes play an important role in peroxide resistance in B. fragilis . Under anaerobic conditions, we observed increases in the number of spontaneous fusidic acid-resistant mutants of five- and sevenfold in ahpCF and ahpF strain backgrounds, respectively, and eightfold in the ahpCF katB double mutant strain compared to the parent and katB strains. In addition, ahpCF , ahpF , and ahpCF katB mutants were slightly more sensitive to oxygen exposure than the parent strain. Moreover, the isolation of a strain with enhanced aerotolerance and high-level resistance to alkyl hydroperoxides from an ahpCF katB parent suggests that the physiological responses to peroxide toxicity and to the toxic effects of molecular oxygen are overlapping and complex in this obligate anaerobe.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.181.18.5701-5710.1999
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1999
    detail.hit.zdb_id: 1481988-0
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 9
    Online Resource
    Online Resource
    The Redox-Sensitive Transcriptional Activator OxyR Regulates the Peroxide Response Regulon in the Obligate Anaerobe Bacteroides fragilis
    American Society for Microbiology ; 2000
    In:  Journal of Bacteriology Vol. 182, No. 18 ( 2000-09-15), p. 5059-5069
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 182, No. 18 ( 2000-09-15), p. 5059-5069
    Abstract: The peroxide response-inducible genes ahpCF , dps , and katB in the obligate anaerobe Bacteroides fragilis are controlled by the redox-sensitive transcriptional activator OxyR. This is the first functional oxidative stress regulator identified and characterized in anaerobic bacteria. oxyR and dps were found to be divergently transcribed, with an overlap in their respective promoter regulatory regions. B. fragilis OxyR and Dps proteins showed high identity to homologues from a closely related anaerobe, Porphyromonas gingivalis . Northern blot analysis revealed that oxyR was expressed as a monocistronic 1-kb mRNA and that dps mRNA was approximately 500 bases in length. dps mRNA was induced over 500-fold by oxidative stress in the parent strain and was constitutively induced in the peroxide-resistant mutant IB263. The constitutive peroxide response in strain IB263 was shown to have resulted from a missense mutation at codon 202 (GAT to GGT) of the oxyR gene [ oxyR (Con)] with a predicted D202G substitution in the OxyR protein. Transcriptional fusion analysis revealed that deletion of oxyR abolished the induction of ahpC and katB following treatment with hydrogen peroxide or oxygen exposure. However, dps expression was induced approximately fourfold by oxygen exposure in Δ oxyR strains but not by hydrogen peroxide. This indicates that dps expression is also under the control of an oxygen-dependent OxyR-independent mechanism. Complementation of Δ oxyR mutant strains with wild-type oxyR and oxyR (Con) restored the inducible peroxide response and the constitutive response of the ahpCF , katB , and dps genes, respectively. However, overexpression of OxyR abolished the catalase activity but not katB expression, suggesting that higher levels of intracellular OxyR may be involved in other physiological processes. Analysis of oxyR expression in the parents and in Δ oxyR and overexpressing oxyR strains by Northern blotting and oxyR ′:: xylB fusions revealed that B. fragilis OxyR does not control its own expression.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.182.18.5059-5069.2000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2000
    detail.hit.zdb_id: 1481988-0
    SSG: 12
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 10
    Online Resource
    Online Resource
    The Bacteroides fragilis transcriptome response to oxygen and H 2 O 2 : the role of OxyR and its effect on survival and virulence
    Wiley ; 2008
    In:  Molecular Microbiology Vol. 67, No. 1 ( 2008-01), p. 129-142
    Details
    In: Molecular Microbiology, Wiley, Vol. 67, No. 1 ( 2008-01), p. 129-142
    Abstract: The intestinal anaerobic symbiont, Bacteroides fragilis , is highly aerotolerant and resistant to H 2 O 2 . Analysis of the transcriptome showed that expression of 45% of the genome was significantly affected by oxidative stress. The gene expression patterns suggested that exposure to oxidative stress induced an acute response to rapidly minimize the immediate effects of reactive oxygen species, then upon extended exposure a broad metabolic response was induced. This metabolic response induced genes encoding enzymes that can supply reducing power for detoxification and restore energy‐generating capacity. An integral aspect of the metabolic response was downregulation of genes related to translation and biosynthesis which correlated with decreased growth and entry into a stationary phase‐like growth state. Examination of oxyR mutants showed that they were impaired for the acute response and they induced the expanded metabolic response with only minimal exposure to stress. The oxyR mutants were more sensitive to oxidants in vitro and in vivo they were attenuated in an intra‐abdominal abscess infection model. Aerotolerance and resistance to oxidative stress are physiological adaptations of B. fragilis to its environment that enhance survival in extra‐intestinal sites and promote opportunistic infections.
    Type of Medium: Online Resource
    ISSN: 0950-382X , 1365-2958
    URL: Issue
    URL: Article
    DOI: 10.1111/mmi.2008.67.issue-1
    DOI: 10.1111/j.1365-2958.2007.06031.x
    Language: English
    Publisher: Wiley
    Publication Date: 2008
    detail.hit.zdb_id: 1501537-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...