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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of Superoxide dismutase genes from Gram-positive bacteria by polymerase chain reaction using degenerate primers (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 131 (1995), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract An internal fragment representing approximately 85% of sod genes from seven Gram-positive bacteria was amplified by using degenerate primers in a polymerase chain reaction assay. The DNA sequences of sod polymerase chain reaction products from Clostridium perfringens, Enterococcus faecalis, Enterococcus faecium, Lactococcus lactis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae, and Streptococcus pyogenes were determined. Comparisons of their deduced amino acid sequences with those of the corresponding regions of the SOD proteins from Bacillus stearothermophilus, Listeria monocytogenes, and Streptococcus mutans revealed strong relatedness. Phylogenetic analysis of SOD peptides showed that members of the genera Streptococcus and those of the genera Enterococcus constitute two well-supported monophyletic groups. The method described in this study provides a means for easy recovery of sod genes and the construction of sod mutants of various Gram-positive pathogens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1995.tb07751.x
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  • 2
    Electronic Resource
    Electronic Resource
    Heterogeneric conjugal transfer of the pheromone-responsive plasmid pIP964 (IncHlyI) of Enterococcus faecalis in the apparent absence of pheromone induction (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 122 (1994), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Erythromycin-resistant derivatives of the pheromone-responsive plasmid pIP964 from Enterococcus faecalis were constructed to study its host range. This was done by inserting the integrative vector pAT112 and the related replicon pTCR1 harboring oriR of the broad host range plasmid pAMβ1 into the hemolysin-bacteriocin operon of pIP964, to give pTCR2 and pTCR3, respectively. Plasmid pTCR2 was transferred by filter matings from E. faecalis to Enterococcus faecium and Listeria monocytogenes at frequencies of 2×10−7 and 5×10−7 per donor, respectively, in the apparent absence of pheromone induction and cellular aggregation. In these hosts, pTCR2 remained intact as a self-replicating element and maintained its transfer capabilities. Plasmid pTCR3, but not pTCR2, was transferred at similar frequencies from E. faecalis to Lactococcus lactis and Streptococcus agalactiae. Thus, the transfer system of pIP964 possesses a broader host-range than its replication system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb07161.x
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  • 3
    Electronic Resource
    Electronic Resource
    Respiration metabolism of Group B Streptococcus is activated by environmental haem and quinone and contributes to virulence (2005)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 56 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Group B Streptococcus (GBS) is a common constituent of the vaginal microflora, but its transmission to newborns can cause life-threatening sepsis, pneumonia and meningitis. Energy metabolism of this opportunist pathogen has been deduced to be strictly fermentative. We discovered that GBS undergoes respiration metabolism if its environment supplies two essential respiratory components: quinone and haem. Respiration metabolism led to significant changes in growth characteristics, including a doubling of biomass and an altered metabolite profile under the tested conditions. The GBS respiratory chain is inactivated by: (i) withdrawing haem and/or quinone, (ii) treating cultures with a respiration inhibitor or (iii) inactivating the cydA gene product, a subunit of cytochrome bd quinol oxidase, in all cases resulting in exclusively fermentative growth. cydA inactivation reduced GBS growth in human blood and strongly attenuated virulence in a neonatal rat sepsis model, suggesting that the animal host may supply the components that activate GBS respiration. These results suggest a role of respiration metabolism in GBS dissemination. Our findings show that environmental factors can increase the flexibility of GBS metabolism by activating a newly identified respiration chain. The need for two environmental factors may explain why GBS respiration metabolism was not found in previous studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2005.04555.x
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  • 4
    Electronic Resource
    Electronic Resource
    A broad-host-range mobilizable shuttle vector for the construction of transcriptional fusions to β-galactosidase in Gram-positive bacteria (1997)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 156 (1997), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A low-copy-number vector designated pTCV-lac has been constructed to provide a convenient system to analyze regulatory elements in Gram-positive bacteria. The main components of this vector are: (i) the origins of replication of pACYC184 and of the broad-host-range enterococcal plasmid pAMβ1, (ii) erythromycin- and kanamycin-resistance-encoding genes for selection in Gram-negative and Gram-positive bacteria, (iii) the transfer origin of the IncP plasmid RK2, and (iv) a promoterless β-galactosidase-encoding lacZ gene with a Gram-positive ribosome binding site. This 12 kb plasmid is present in Gram-positive hosts in three to five copies per chromosome equivalent and contains three unique cloning sites (EcoRI, SmaI, BamHI) for cloning of DNA inserts upstream of the lacZ gene. Plasmid pTCV-lac and derivatives carrying different promoter fragments have been transferred by conjugation from an Escherichia coli IncP mobilizing donor strain to Bacillus subtilis, Listeria monocytogenes, Enterococcus faecalis, and Streptococcus agalactiae. These plasmids were structurally stable in these hosts and the corresponding promoter activities, quantitated by the determination of the β-galactosidase specific activities, were found to cover at least a 100-fold range in β-galactosidase values. These results indicate that pTCV-lac should be useful for analysis of gene regulation in a wide range of Gram-positive bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1997.tb12726.x
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of D-alanyl-lipoteichoic acid is required for adhesion and virulence of Listeria monocytogenes (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The dlt operon of Gram-positive bacteria comprises four genes (dltA, dltB, dltC and dltD) that catalyse the incorporation of D-alanine residues into the cell wall-associated lipoteichoic acids (LTAs). In this work, we characterized the dlt operon of Listeria monocytogenes and constructed a D-Ala-deficient LTA mutant by inactivating the first gene (dltA) of this operon. The DltA− mutant did not show any morphological alterations and its growth rate was similar to that of the wild-type strain. However, it exhibited an increased susceptibility to the cationic peptides colistin, nisin and polymyxin B. The virulence of the DltA− mutant was severely impaired in a mouse infection model (4 log increase in the LD50) and, in vitro, the adherence of the mutant to various cell lines (murine bone marrow-derived macrophages and hepatocytes and a human epithelial cell line) was strongly restricted, although the amounts of surface proteins implicated in virulence (ActA, InlA and InlB) remains unaffected. We suggest that the decreased adherence of the DltA− mutant to non-phagocytic and phagocytic cells might be as a result of the increased electronegativity of its charge surface and/or the presence at the bacterial surface of adhesins possessing altered binding activities. These results show that the D-alanylation of the LTAs contributes to the virulence of the intracellular pathogen L. monocytogenes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02723.x
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  • 6
    Electronic Resource
    Electronic Resource
    Attenuated virulence of Streptococcus agalactiae deficient in D-alanyl-lipoteichoic acid is due to an increased susceptibility to defensins and phagocytic cells (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: D-alanylation of lipoteichoic acid (LTA), allows Gram-positive bacteria to modulate their surface charge, regulate ligand binding and control the electromechanical properties of the cell wall. In this study, the role of D-alanyl LTA in the virulence of the extracellular pathogen Streptococcus agalactiae was investigated. We demonstrate that a DltA– isogenic mutant displays an increased susceptibility to host defence peptides such as human defensins and animal-derived cationic peptides. Accordingly, the mutant strain is more susceptible to killing by mice bone marrow-derived macrophages and human neutrophils than the wild-type strain. In addition, the virulence of the DltA– mutant is severely impaired in mouse and neonatal rat models. This mutant was eliminated more rapidly than the wild-type strain from the lung of three-week-old mice inoculated intranasally and, consequently, is unable to induce a pneumonia. Finally, after intravenous injection of three-week-old mice, the survival of the DltA– mutant is markedly reduced in the blood in comparison to that of the wild-type strain. We hypothesize that the decreased virulence of the DltA– mutant is a consequence of its increased susceptibility to cationic antimicrobial peptides and to killing by phagocytes. These results demonstrate that the D-alanylation of LTA contributes to the virulence of S. agalactiae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03655.x
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  • 7
    Electronic Resource
    Electronic Resource
    CovS/CovR of group B streptococcus: a two-component global regulatory system involved in virulence (2004)
    Oxford, UK : Blackwell Publishing Ltd.
    Molecular microbiology 54 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In this study, we carried out a detailed structural and functional analysis of a Streptococcus agalactiae (GBS) two-component system which is orthologous to the CovS/CovR (CsrS/CsrR) regulatory system of Streptococcus pyogenes. In GBS, covR and covS are part of a seven gene operon transcribed from two promoters that are not regulated by CovR. A ΔcovSR mutant was found to display dramatic phenotypic changes such as increased haemolytic activity and reduced CAMP activity on blood agar. Adherence of the ΔcovSR mutant to epithelial cells was greatly increased and analysis by transmission electron microscopy revealed the presence at its surface of a fibrous extracellular matrix that might be involved in these intercellular interactions. However, the ΔcovSR mutant was unable to initiate growth in RPMI and its viability in human normal serum was greatly impaired. A major finding of this phenotypic analysis was that the CovS/CovR system is important for GBS virulence, as a 3 log increase of the LD50 of the mutant strain was observed in the neonate rat sepsis model. The pleiotropic phenotype of the ΔcovSR mutant is in full agreement with the large number of genes controlled by CovS/CovR as seen by expression profiling analysis, many of which encode potentially secreted or cell surface-associated proteins: 76 genes are repressed whereas 63 were positively regulated. CovR was shown to bind directly to the regulatory regions of several of these genes and a consensus CovR recognition sequence was proposed using both DNase I footprinting and computational analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04365.x
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  • 8
    Electronic Resource
    Electronic Resource
    Genome sequence of Streptococcus agalactiae, a pathogen causing invasive neonatal disease (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 45 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Streptococcus agalactiae is a commensal bacterium colonizing the intestinal tract of a significant proportion of the human population. However, it is also a pathogen which is the leading cause of invasive infections in neonates and causes septicaemia, meningitis and pneumonia. We sequenced the genome of the serogroup III strain NEM316, responsible for a fatal case of septicaemia. The genome is 2 211 485 base pairs long and contains 2118 protein coding genes. Fifty-five per cent of the predicted genes have an ortholog in the Streptococcus pyogenes genome, representing a conserved backbone between these two streptococci. Among the genes in S. agalactiae that lack an ortholog in S. pyogenes , 50% are clustered within 14 islands. These islands contain known and putative virulence genes, mostly encoding surface proteins as well as a number of genes related to mobile elements. Some of these islands could therefore be considered as pathogenicity islands. Compared with other pathogenic streptococci, S. agalactiae shows the unique feature that pathogenicity islands may have an important role in virulence acquisition and in genetic diversity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.03126.x
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  • 9
    Electronic Resource
    Electronic Resource
    Listeriolysin O-dependent activation of endothelial cells during infection with Listeria monocytogenes: activation of NF-κB and upregulation of adhesion molecules and chemokines (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The facultative intracellular bacterium Listeria monocytogenes is an invasive pathogen that crosses the vascular endothelium and disseminates to the placenta and the central nervous system. Its interaction with endothelial cells is crucial for the pathogenesis of listeriosis. By infecting in vitro human umbilical vein endothelial cells (HUVEC) with L. monocytogenes, we found that wild-type bacteria induced the expression of the adhesion molecules (ICAM-1 and E-selectin), chemokine secretion (IL-8 and monocyte chemotactic protein-1) and NF-κB nuclear translocation. The activation of HUVEC required viable bacteria and was abolished in prfA-deficient mutants of L. monocytogenes, suggesting that virulence genes are associated with endothelial cell activation. Using a genetic approach with mutants of virulence genes, we found that listeriolysin O (LLO)-deficient mutants inactivated in the hly gene did not induce HUVEC activation, as opposed to mutants inactivated in the other virulence genes. Adhesion molecule expression, chemokine secretion and NF-κB activation were fully restored by a strain of Listeria innocua transformed with the hly gene encoding LLO. The relevance in vivo of endothelial cell activation for listerial pathogenesis was investigated in transgenic mice carrying an NF-κB-responsive lacZ reporter gene. NF-κB activation was visualized by a strong lacZ expression in endothelial cells of capillaries of mice infected with a virulent haemolytic strain, but was not seen in those infected with a non-haemolytic isogenic mutant. Direct evidence that LLO is involved in NF-κB activation in transgenic mice was provided by injecting intravenously purified LLO, thus inducing stimulation of NF-κB in endothelial cells of blood capillaries. Our results demonstrate that functional listeriolysin O secreted by bacteria contributes as a potent inflammatory stimulus to inducing endothelial cell activation during the infectious process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01305.x
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  • 10
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    Colorectal cancer specific conditions promote Streptococcus gallolyticus gut colonization (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-12-26
    Description: Colonization by Streptococcus gallolyticus subsp. gallolyticus (SGG) is strongly associated with the occurrence of colorectal cancer (CRC). However, the factors leading to its successful colonization are unknown, and whether SGG influences the oncogenic process or benefits from the tumor-prone environment to prevail remains an open question. Here, we elucidate crucial steps that explain how CRC favors SGG colonization. By using mice genetically prone to CRC, we show that SGG colonization is 1,000-fold higher in tumor-bearing mice than in normal mice. This selective advantage occurs at the expense of resident intestinal enterococci. An SGG-specific locus encoding a bacteriocin (“gallocin”) is shown to kill enterococci in vitro. Importantly, bile acids strongly enhance this bacteriocin activity in vivo, leading to greater SGG colonization. Constitutive activation of the Wnt pathway, one of the earliest signaling alterations in CRC, and the decreased expression of the bile acid apical transporter gene Slc10A2, as an effect of the Apc founding mutation, may thereby sustain intestinal colonization by SGG. We conclude that CRC-specific conditions promote SGG colonization of the gut by replacing commensal enterococci in their niche.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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