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Multiple mechanisms for the activation of human platelet aggregation by Staphylococcus aureus: roles for the clumping factors ClfA and ClfB, the serine–aspartate repeat protein SdrE and protein A (2002)

O´Brien, Louise ; Kerrigan, Steven W. ; Kaw, Gideon ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 44 (2002), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: The ability of Staphylococcus aureus cells to induce platelet aggregation has long been recognized. However, despite several attempts to identify the mechanisms involved in this interaction, the nature of the bacterial receptors required remains poorly understood. Using genetic manipulation, this study for the first time provides clear evidence that several S. aureus surface proteins participate in the inter-action with platelets. Mutants of S. aureus strain Newman lacking one or more surface proteins were tested for their ability to stimulate platelet aggre-gation. This approach was complemented by the expression of a number of candidate proteins in the non-aggregating Gram-positive bacterium Lacto-coccus lactis. S. aureus-induced aggregation was monophasic and was dependent on the platelet receptor GPIIb/IIIa. The fibrinogen-binding proteins, clumping factors A and B and the serine-aspartate repeat protein SdrE could each induce aggregation when expressed in L. lactis. Although protein A expressed in L. lactis was not capable of inducing aggregation independently, it enhanced the aggregation response when expressed on the surface of S. aureus. Thus, S. aureus has multiple mechanisms for stimulating platelet aggregation. Such functional redundancy suggests that this phenomenon may be important in the pathogenesis of invasive diseases such as infective endocarditis.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02935.x

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Sip, an integrase protein with excision, circularization and integration activities, defines a new family of mobile Staphylococcus aureus pathogenicity islands (2003)

Úbeda, Carles ; Tormo, Ma. Ángeles ; Cucarella, Carme ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 49 (2003), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: We report the complete sequence of Staphylococcal pathogenicity island bovine 2 (SaPIbov2), encoding the biofilm-associated protein Bap. SaPIbov2 contains 24 open reading frames, including sip, which encodes a functional staphylococcal integrase protein. SaPIbov2 is bordered by 18 bp direct repeats. The integration site into the chromosome lies at the 3′ end of a gene encoding GMP synthase. SaPIbov2 has extensive similarity to previously described pathogenicity islands of Staphylococcus aureus. The principal difference is that toxin genes present in the other pathogenicity islands are exchanged for a transposon-like element that carries the bap gene and genes encoding an ABC transporter and a transposase. Also, SaPIbov2 can be excised to form a circular element and can integrate site-specifically and RecA-independently at a chromosomal att site in a Sip-dependent manner. This was demonstrated both in S. aureus and with plasmid substrates ectopically in Escherichia coli. Thus, SaPIbov2 encodes a functional recombinase of the integrase family that promotes element excision and insertion/integration. In addition, we demonstrated that the presence of SaPIbov2 facilitated the persistence of S. aureus in an intramammary gland infection model. Finally, different bovine isolates of S. aureus were found to carry islands related to SaPIbov2, suggesting the existence of a family of related pathogenicity islands.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03577.x

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BapA, a large secreted protein required for biofilm formation and host colonization of Salmonella enterica serovar Enteritidis (2005)

Latasa, Cristina ; Roux, Agnès ; Toledo-Arana, Alejandro ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 58 (2005), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: In environmental settings, biofilms represent the common way of life of microorganisms. Salmonella enterica serovar Enteritidis, the most frequent cause of gastroenteritis in developed countries, produces a biofilm whose matrix is mainly composed of curli fimbriae and cellulose. In contrast to other bacterial biofilms, no proteinaceous compound has been reported to participate in the formation of this matrix. Here, we report the discovery of BapA, a large cell-surface protein required for biofilm formation by S. Enteritidis. Deletion of bapA caused the loss of the capacity to form a biofilm whereas the overexpression of a chromosomal copy of bapA increased the biofilm biomass formation. We provide evidence that overproduction of curli fimbriae and not cellulose can compensate for the biofilm deficiency of a bapA mutant strain. BapA is secreted through a type I protein secretion system (BapBCD) situated downstream of the bapA gene and was found to be loosely associated with the cell surface. Experiments with mixed bacterial populations positive or negative for BapA showed that BapA minus cells are not recruited into the biofilm matrix. The expression of bapA is coordinated with that of genes encoding curli fimbriae and cellulose, through the action of csgD. Studies on the contribution of BapA to S. Enteritidis pathogenesis revealed that orally inoculated animals with a bapA-deficient strain survived longer than those inoculated with the wild-type strain. Also, a bapA mutant strain showed a significantly lower colonization rate at the intestinal cell barrier and consequently a decreased efficiency for organ invasion compared with the wild-type strain. Taken together, these data demonstrate that BapA contributes both to biofilm formation and invasion through the regular Salmonella infection route.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04907.x

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Antibiotic-induced SOS response promotes horizontal dissemination of pathogenicity island-encoded virulence factors in staphylococci (2005)

Úbeda, Carles ; Maiques, Elisa ; Knecht, Erwin ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 56 (2005), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Although mobile genetic elements have a crucial role in spreading pathogenicity-determining genes among bacterial populations, environmental and genetic factors involved in the horizontal transfer of these genes are largely unknown. Here we show that SaPIbov1, a Staphylococcus aureus pathogenicity island that belongs to the growing family of these elements that are found in many strains, is induced to excise and replicate after SOS induction of at least three different temperate phages, 80α, φ11 and φ147, and is then packaged into phage-like particles and transferred at high frequency. SOS induction by commonly used fluoroquinolone antibiotics, such as ciprofloxacin, also results in replication and high-frequency transfer of this element, as well as of SaPI1, the prototypical island of S. aureus, suggesting that such antibiotics may have the unintended consequence of promoting the spread of bacterial virulence factors. Although the strains containing these prophages do not normally contain SaPIs, we have found that RF122-1, the original SaPIbov1-containing clinical isolate, contains a putative second pathogenicity island that is replicated after SOS induction, by antibiotic treatment, of the prophage(s) present in the strain. Although SaPIbov1 is not induced to replicate after SOS induction in this strain, it is transferred by the antibiotic-activated phages. We conclude that SOS induction by therapeutic agents can promote the spread of staphylococcal virulence genes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04584.x

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SarA and not σB is essential for biofilm development by Staphylococcus aureus (2003)

Valle, Jaione ; Toledo-Arana, Alejandro ; Berasain, Carmen ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 48 (2003), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Staphylococcus aureus biofilm formation is associated with the production of the polysaccharide intercellular adhesin (PIA/PNAG), the product of the ica operon. The staphylococcal accessory regulator, SarA, is a central regulatory element that controls the production of S. aureus virulence factors. By screening a library of Tn917 insertions in a clinical S. aureus strain, we identified SarA as being essential for biofilm development. Non-polar mutations of sarA in four genetically unrelated S. aureus strains decreased PIA/PNAG production and completely impaired biofilm development, both in steady state and flow conditions via an agr-independent mechanism. Accordingly, real-time PCR showed that the mutation in the sarA gene resulted in downregulation of the ica operon transcription. We also demonstrated that complete deletion of σB did not affect PIA/PNAG production and biofilm formation, although it slightly decreased ica operon transcription. Furthermore, the sarA-σB double mutant showed a significant decrease of ica expression but an increase of PIA/PNAG production and biofilm formation compared to the sarA single mutant. We propose that SarA activates S. aureus development of biofilm by both enhancing the ica operon transcription and suppressing the transcription of either a protein involved in the turnover of PIA/PNAG or a repressor of its synthesis, whose expression would be σB-dependent.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03493.x

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6

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Block and asynchronous two-stage methods for mildly nonlinear systems (1999)

Bai, Zhong-Zhi ; Migallón, Violeta ; Penadés, José ; [et al.]

Springer

Numerische Mathematik 82 (1999), S. 1-20

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ISSN: 0945-3245

Keywords: Mathematics Subject Classification (1991):65H10, 65F10

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract. Block parallel iterative methods for the solution of mildly nonlinear systems of equations of the form $Ax=\Phi(x)$ are studied. Two-stage methods, where the solution of each block is approximated by an inner iteration, are treated. Both synchronous and asynchronous versions are analyzed, and both pointwise and blockwise convergence theorems provided. The case where there are overlapping blocks is also considered. The analysis of the asynchronous method when applied to linear systems includes cases not treated before in the literature.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s002110050409

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7

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Hydrophobicity of ruminant mastitisStaphylococcus aureus in relation to bacterial aging and slime production (1992)

Baselga, Rafael ; Albizu, Iñaki ; Penadés, José Rafael ; [et al.]

Springer

Current microbiology 25 (1992), S. 173-179

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ISSN: 1432-0991

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract Hydrophobicity of 72 bovine and 53 ovine mastitisStaphylococcus aureus strains was studied throughout the logarithmic growth phase with a water-xylene two-phase system. Hydrophobicity increased during this growth phase. Freshly isolated strains were more hydrophobic than old strains (p〈0.01). Old (bovine) strains became more hydrophobic (i.e., “refreshed”) after passage through the mouse mammary gland (p〈0.01). Bovine strains were more hydrophobic than ovine strains (p〈0.01). For the majority of strains, bacteria became more hydrophilic (p〈0.001) after growth in exopolysaccharide-inducing media (Columbia and modifiedStaphylococcus 110 broth). This could be expected, since exopolysaccharides are hydrophilic. However, in these media, the strains that were able to produce slime in Congo red agar or in tryptic soy broth supplemented with 2% glucose (w/v) did not become more hydrophilic. It is proposed that different mechanisms may be involved in triggering exopolysaccharide production when different exopolysaccharide-inducing media are used.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01571026

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8

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Block Two-stage Methods for Singular Systems and Markov Chains (1996)

Migallón, Violeta ; Penadés, José ; Szyld, Daniel B.

New York, NY [u.a.] : Wiley-Blackwell

Numerical Linear Algebra with Applications 3 (1996), S. 413-426

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ISSN: 1070-5325

Keywords: iterative methods ; linear systems ; singular matrices ; block methods ; multisplitting ; two-stage ; non-stationary ; Markov chains ; Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mathematics

Notes: The use of block two-stage methods for the iterative solution of consistent singular linear systems is studied. In these methods, suitable for parallel computations, different blocks, i.e., smaller linear systems, can be solved concurrently by different processors. Each of these smaller systems are solved by an (inner) iterative method. Hypotheses are provided for the convergence of non-stationary methods, i.e., when the number of inner iterations may vary from block to block and from one outer iteration to another. It is shown that the iteration matrix corresponding to one step of the block method is convergent, i.e., that its powers converge to a limit matrix. A theorem on the convergence of the infinite product of matrices with the same eigenspace corresponding to the eigenvalue 1 is proved, and later used as a tool in the convergence analysis of the block method. The methods studied can be used to solve any consistent singular system, including discretizations of certain differential equations. They can also be used to find stationary probability distribution of Markov chains. This last application is considered in detail.

Type of Medium: Electronic Resource

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