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  • American Society for Microbiology  (4)
  • 1
    Online Resource
    Online Resource
    Role of Quorum Sensing and Antimicrobial Component Production by Serratia plymuthica in Formation of Biofilms, Including Mixed Biofilms with Escherichia coli
    American Society for Microbiology ; 2006
    In:  Applied and Environmental Microbiology Vol. 72, No. 11 ( 2006-11), p. 7294-7300
    Details
    In: Applied and Environmental Microbiology, American Society for Microbiology, Vol. 72, No. 11 ( 2006-11), p. 7294-7300
    Abstract: We have previously characterized the N -acyl- l -homoserine lactone-based quorum-sensing system of the biofilm isolate Serratia plymuthica RVH1. Here we investigated the role of quorum sensing and of quorum-sensing-dependent production of an antimicrobial compound (AC) on biofilm formation by RVH1 and on the cocultivation of RVH1 and Escherichia coli in planktonic cultures or in biofilms. Biofilm formation of S. plymuthica was not affected by the knockout of splI or splR , the S. plymuthica homologs of the luxI or luxR quorum-sensing gene, respectively, or by the knockout of AC production. E. coli grew well in mixed broth culture with RVH1 until the latter reached 8.5 to 9.5 log CFU/ml, after which the E. coli colony counts steeply declined. In comparison, only a very small decline occurred in cocultures with the S. plymuthica AC-deficient and splI mutants. Complementation with exogenous N -hexanoyl- l -homoserine lactone rescued the wild-type phenotype of the splI mutant. The splR knockout mutant also induced a steep decline of E. coli , consistent with its proposed function as a repressor of quorum-sensing-regulated genes. The numbers of E. coli in 3-day-old mixed biofilms followed a similar pattern, being higher with S. plymuthica deficient in SplI or AC production than with wild-type S. plymuthica , the splR mutant, or the splI mutant in the presence of N -hexanoyl- l -homoserine lactone. Confocal laser scanning microscopic analysis of mixed biofilms established with strains producing different fluorescent proteins showed that E. coli microcolonies were less developed in the presence of RVH1 than in the presence of the AC-deficient mutant.
    Type of Medium: Online Resource
    ISSN: 0099-2240 , 1098-5336
    URL: Article
    DOI: 10.1128/AEM.01708-06
    RVK:
    WA 15000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 223011-2
    detail.hit.zdb_id: 1478346-0
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Development of Resistance against Diketo Derivatives of Human Immunodeficiency Virus Type 1 by Progressive Accumulation of Integrase Mutations
    American Society for Microbiology ; 2003
    In:  Journal of Virology Vol. 77, No. 21 ( 2003-11), p. 11459-11470
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 77, No. 21 ( 2003-11), p. 11459-11470
    Abstract: The diketo acid L-708,906 has been reported to be a selective inhibitor of the strand transfer step of the human immunodeficiency virus type 1 (HIV-1) integration process (D. Hazuda, P. Felock, M. Witmer, A. Wolfe, K. Stillmock, J. A. Grobler, A. Espeseth, L. Gabryelski, W. Schleif, C. Blau, and M. D. Miller, Science 287:646-650, 2000). We have now studied the development of antiviral resistance to L-708,906 by growing HIV-1 strains in the presence of increasing concentrations of the compound. The mutations T66I, L74M, and S230R emerged successively in the integrase gene. The virus with three mutations (T66I L74M S230R) was 10-fold less susceptible to L-708,906, while displaying the sensitivity of the wild-type virus to inhibitors of the RT or PRO or viral entry process. Chimeric HIV-1 strains containing the mutant integrase genes displayed the same resistance profile as the in vitro-selected strains, corroborating the impact of the reported mutations on the resistance phenotype. Phenotypic cross-resistance to S-1360, a diketo analogue in clinical trials, was observed for all strains. Interestingly, the diketo acid-resistant strain remained fully sensitive to V-165, a novel integrase inhibitor (C. Pannecouque, W. Pluymers, B. Van Maele, V. Tetz, P. Cherepanov, E. De Clercq, M. Witvrouw, and Z. Debyser, Curr. Biol. 12:1169-1177, 2002). Antiviral resistance was also studied at the level of recombinant integrase. Single mutations did not appear to impair specific enzymatic activity. However, 3′ processing and strand transfer activities of the recombinant integrases with two (T66I L74M) and three (T66I L74M S230R) mutations were notably lower than those of the wild-type integrase. Although the virus with three mutations was resistant to inhibition by diketo acids, the sensitivity of the corresponding enzyme to L-708,906 or S-1360 was reduced only two- to threefold. As to the replication kinetics of the selected strains, the replication fitness for all strains was lower than that of the wild-type HIV-1 strain.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.77.21.11459-11470.2003
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2003
    detail.hit.zdb_id: 1495529-5
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  • 3
    Online Resource
    Online Resource
    Overexpression of the Lens Epithelium-Derived Growth Factor/p75 Integrase Binding Domain Inhibits Human Immunodeficiency Virus Replication
    American Society for Microbiology ; 2006
    In:  Journal of Virology Vol. 80, No. 23 ( 2006-12), p. 11498-11509
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 80, No. 23 ( 2006-12), p. 11498-11509
    Abstract: We initially identified lens epithelium-derived growth factor/p75 (LEDGF/p75) as a binding partner of human immunodeficiency virus type 1 (HIV-1) integrase. To investigate the role of LEDGF/p75 in HIV replication and its potential as a new antiviral target, we stably overexpressed two different fragments containing the integrase binding domain (IBD) of LEDGF/p75 fused to enhanced green fluorescent protein (eGFP). HIV-1 replication was severely inhibited by overexpression of the eGFP-IBD fusion proteins, while no inhibition was observed in cell lines overexpressing the interaction-deficient D366A mutant. Quantitative PCR pinpointed the block to the integration step, whereas nuclear import was not affected. Competition of the IBD fusion proteins with endogenous LEDGF/p75 for binding to integrase led to a potent defect in HIV-1 replication in both HeLaP4- and MT-4-derived cell lines. A previously described diketo acid-resistant HIV-1 strain remained fully susceptible to inhibition, suggesting that this strategy will also work in patients who harbor strains resistant to the current experimental integrase inhibitors. These data support LEDGF/p75 as an important cofactor for HIV replication and provide proof of concept for the LEDGF/p75-integrase interaction as a novel target for treating HIV-1 infection.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.00801-06
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1495529-5
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  • 4
    Online Resource
    Online Resource
    Membrane Topology of the Streptomyces lividans Type I Signal Peptidases
    American Society for Microbiology ; 2001
    In:  Journal of Bacteriology Vol. 183, No. 16 ( 2001-08-15), p. 4752-4760
    Details
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 183, No. 16 ( 2001-08-15), p. 4752-4760
    Abstract: Most bacterial membranes contain one or two type I signal peptidases (SPases) for the removal of signal peptides from export proteins. For Streptomyces lividans , four different type I SPases (denoted SipW, SipX, SipY, and SipZ) were previously described. In this communication, we report the experimental determination of the membrane topology of these SPases. A protease protection assay of SPase tendamistat fusions confirmed the presence of the N- as well as the C-terminal transmembrane anchor for SipY. SipX and SipZ have a predicted topology similar to that of SipY. These three S. lividans SPases are currently the only known prokaryotic-type type I SPases of gram-positive bacteria with a C-terminal transmembrane anchor, thereby establishing a new subclass of type I SPases. In contrast, S. lividans SipW contains only the N-terminal transmembrane segment, similar to most type I SPases of gram-positive bacteria. Functional analysis showed that the C-terminal transmembrane anchor of SipY is important to enhance the processing activity, both in vitro as well as in vivo. Moreover, for the S. lividans SPases, a relation seems to exist between the presence or absence of the C-terminal anchor and the relative contributions to the total SPase processing activity in the cell. SipY and SipZ, two SPases with a C-terminal anchor, were shown to be of major importance to the cell. Accordingly, for SipW, missing the C-terminal anchor, a minor role in preprotein processing was found.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    URL: Article
    DOI: 10.1128/JB.183.16.4752-4760.2001
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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