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  • 1
    Electronic Resource
    Electronic Resource
    Raymond Dedonder 1920–2004 (2005)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 55 (2005), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04434.x
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  • 2
    Electronic Resource
    Electronic Resource
    Genes controlled by the essential YycG/YycF two-component system of Bacillus subtilis revealed through a novel hybrid regulator approach (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: The YycG/YycF two-component system, originally identified in Bacillus subtilis, is very highly conserved and appears to be specific to low G + C Gram-positive bacteria. This system is required for cell viability, although the basis for this and the nature of the YycF regulon remained elusive. Using a combined hybrid regulator/transcriptome approach involving the inducible expression of a PhoP′-′YycF chimerical protein in B. subtilis, we have shown that expression of yocH, which encodes a potential autolysin, is specifically activated by YycF. Gel mobility shift and DNase I footprinting assays were used to show direct binding in vitro of purified YycF to the regulatory regions of yocH as well as ftsAZ, previously reported to be controlled by YycF. Nucleotide sequence analysis and site-directed mutagenesis allowed us to define a potential consensus recognition sequence for the YycF response regulator, composed of two direct repeats: 5′-TGT A/T A A/T/C-N5-TGT A/T A A/T/C-3′. A DNA-motif analysis indicates that there are potentially up to 10 genes within the B. subtilis YycG/YycF regulon, mainly involved in cell wall metabolism and membrane protein synthesis. Among these, YycF was shown to bind directly to the region upstream from the ykvT gene, encoding a potential cell wall hydrolase, and the intergenic region of the tagAB/tagDEF divergon, encoding essential components of teichoic acid biosynthesis. Definition of a potential YycF recognition sequence allowed us to identify likely members of the YycF regulon in other low G + C Gram-positive bacteria, including several pathogens such as Listeria monocytogenes, Staphylococcus aureus and Streptococcus pneumoniae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03661.x
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  • 3
    Electronic Resource
    Electronic Resource
    A six amino acid deletion, partially overlapping the VanSB G2 ATP-binding motif, leads to constitutive glycopeptide resistance in VanB-type Enterococcus faecium (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 50 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Enterococcus faecium clinical isolate BM4524, resistant to vancomycin and susceptible to teicoplanin, harboured a chromosomal vanB cluster, including the vanS B / vanR B two-component system regulatory genes. Enterococcus faecium strain BM4525, isolated two weeks later from the same patient, was resistant to high levels of both glycopeptides. The ddl gene of BM4525 had a 2 bp insertion leading to an impaired d -alanine: d -alanine ligase. Sequencing of the vanB operon in BM4525 also revealed an 18 bp deletion in the vanS B gene designated vanS BΔ . The resulting six amino acid deletion partially overlapped the G2 ATP-binding domain of the VanS BΔ histidine kinase leading to constitutive expression of the resistance genes. Sequence analysis indicated that the deletion occurred between two tandemly arranged heptanucleotide direct repeats, separated by 11 base-pairs. The VanS B , VanS BΔ and VanR B proteins were overproduced in Escherichia coli and purified. In vitro autophosphorylation of the VanS B and VanS BΔ histidine kinases and phosphotransfer to the VanR B response regulator did not differ significantly. However, VanS BΔ was deficient in VanR B phosphatase activity leading to accumulation of phosphorylated VanR B . Increased glycopeptide resistance in E. faecium BM4525 was therefore a result of the lack of production of d -alanyl- d -alanine ending pentapeptide and to constitutive synthesis of d -alanyl- d -lactate terminating peptidoglycan precursors, following loss of d -alanine: d -alanine ligase and of VanS B phosphatase activity respectively. We suggest that the heptanucleotide direct repeat in vanS B may favour the appearance of high level constitutively expressed vancomycin resistance through a ‘slippage’ type of genetic rearrangement in VanB-type strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03771.x
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  • 4
    Electronic Resource
    Electronic Resource
    Stress induction of the Bacillus subtilis clpP gene encoding a homologue of the proteolytic component of the Clp protease and the involvement of ClpP and ClpX in stress tolerance (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 28 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Bacillus subtilis clpP gene, encoding the proteolytic component of the Clp or Ti protease, was cloned and sequenced. The amount of clpP-specific mRNA increased after heat shock, salt and ethanol stress, as well as after treatment with puromycin. Two transcriptional start sites upstream of the clpP structural gene were identified, preceded by sequences resembling the consensus sequences of promoters recognized by σA andσB transcriptional factors of the B. subtilis RNA polymerase respectively. Transcription initiation occurred predominantly at the putative σA-dependent promoter in exponentially growing cells and was induced under stress conditions. After exposure to stress, initiation of transcription also increased at the σB-dependent promoter, but to a lesser extent, indicating that clpP belongs to a double promoter-controlled subgroup of class III general stress genes in B. subtilis. In a sigB mutant strain, clpP remained heat and stress inducible at the σA-dependent promoter. BgaB–reporter gene fusions, carrying either the σA- or the σB-dependent promoter, showed a higher bgaB induction at the σA-dependent promoter, whereas a significantly lower level of induction was measured at the σB-dependent promoter. The σA-dependent promoter appeared to be crucial for the heat-inducible transcription of clpP. A CIRCE (controlling inverted repeat of chaperone expression) element, the characteristic regulation target of class I heat shock genes such as dnaK and groESL, was not found between the transcriptional and translational start sites. Mutants lacking either the proteolytic component ClpP or the regulatory ATPase component ClpX were phenotypically distinct from the wild type. Both mutants produced chains of elongated cells and exhibited severely impaired growth under stress conditions and starvation. Comparison of two-dimensional protein gels from wild-type cells with those from clpP and clpX mutant cells revealed several changes in the protein pattern. Several proteins, such as GroEL, PpiB, PykA, SucD, YhfP, YqkF, YugJ and YvyD, which were found preferentially in higher amounts in both clpP and clpX mutants, might be potential substrates for the ClpXP protease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00840.x
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  • 5
    Electronic Resource
    Electronic Resource
    Clp ATPases are required for stress tolerance, intracellular replication and biofilm formation in Staphylococcus aureus (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: The Hsp100/Clp ATPases constitute a family of closely related proteins of which some members function solely as chaperones whereas others additionally can associate with the unrelated ClpP peptidase forming a Clp proteolytic complex. We have investigated the role of four Clp ATPases in the versatile pathogen, Staphylococcus aureus. Previously, we showed that ClpX is required for expression of major virulence factors and for virulence of S. aureus, but not for survival during heat shock. In the present study, we have inactivated clpC, clpB and clpL and, while none of these mutations affected toxin production, both ClpC and ClpB and to a minor extent ClpL were required for intracellular multiplication within bovine mammary epithelial cells. These defects were paralleled by an inability of the clpC mutant to grow at high temperature and of the clpB mutant to induce thermotolerance indicating that the protective functions of these proteins are required both at high temperature and during infection. By primer extension analysis and footprint studies, we show that expression of clpC and clpB is controlled by the negative heat-shock regulator, CtsR, and that ClpC is required for its repressor activity. Thus, ClpC is a likely sensor of stress encountered during both environmental stress and infection. In addition to virulence factor production the ability to form biofilms is of importance to S. aureus as a nosocomial pathogen. Interestingly, biofilm formation was reduced in the absence of ClpX or ClpC whereas it was enhanced in the absence of ClpP. Thus, our data show that Clp proteolytic complexes and the Clp ATPases control several key processes of importance to the success of S. aureus as a pathogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04368.x
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  • 6
    Electronic Resource
    Electronic Resource
    Comparative genomics reveal novel heat shock regulatory mechanisms in Staphylococcus aureus and other Gram-positive bacteria (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 47 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Multiple regulatory mechanisms for coping with stress co-exist in low G+C Gram-positive bacteria. Among these, the HrcA and CtsR repressors control distinct regulons in the model organism, Bacillus subtilis. We recently identified an orthologue of the CtsR regulator of stress response in the major pathogen, Staphylococcus aureus. Sequence analysis of the S. aureus genome revealed the presence of potential CtsR operator sites not only upstream from genes encoding subunits of the Clp ATP-dependent protease, as in B. subtilis, but also, unexpectedly, within the promoter regions of the dnaK and groESL operons known to be specifically controlled by HrcA. The tandem arrangement of the CtsR and HrcA operators suggests a novel mode of dual heat shock regulation by these two repressors. The S. aureus ctsR and hrcA genes were cloned under the control of the PxylA xylose-inducible promoter and used to demonstrate dual regulation of the dnaK and groESL operons by both CtsR and HrcA, using B. subtilis as a heterologous host. Direct binding by both repressors was shown in vitro by gel mobility shift and DNase I footprinting experiments using purified S. aureus CtsR and HrcA proteins. ΔctsR, ΔhrcA and ΔctsRΔhrcA mutants of S. aureus were constructed, indicating that the two repressors are not redundant but, instead, act together synergistically to maintain low basal levels of expression of the dnaK and groESL operons in the absence of stress. This novel regulatory mode appears to be specific to Staphylococci.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03355.x
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  • 7
    Electronic Resource
    Electronic Resource
    CtsR, a novel regulator of stress and heat shock response, controls clp and molecular chaperone gene expression in Gram-positive bacteria (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: clpP and clpC of Bacillus subtilis encode subunits of the Clp ATP-dependent protease and are required for stress survival, including growth at high temperature. They play essential roles in stationary phase adaptive responses such as the competence and sporulation developmental pathways, and belong to the so-called class III group of heat shock genes, whose mode of regulation is unknown and whose expression is induced by heat shock or general stress conditions. The product of ctsR, the first gene of the clpC operon, has now been shown to act as a repressor of both clpP and clpC, as well as clpE, which encodes a novel member of the Hsp100 Clp ATPase family. The CtsR protein was purified and shown to bind specifically to the promoter regions of all three clp genes. Random mutagenesis, DNaseI footprinting and DNA sequence deletions and comparisons were used to define a consensus CtsR recognition sequence as a directly repeated heptad upstream from the three clp genes. This target sequence was also found upstream from clp and other heat shock genes of several Gram-positive bacteria, including Listeria monocytogenes, Streptococcus salivarius, S. pneumoniae, S. pyogenes, S. thermophilus, Enterococcus faecalis, Staphylococcus aureus, Leuconostoc oenos, Lactobacillus sake, Lactococcus lactis and Clostridium acetobutylicum. CtsR homologues were also identified in several of these bacteria, indicating that heat shock regulation by CtsR is highly conserved in Gram-positive bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01152.x
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  • 8
    Electronic Resource
    Electronic Resource
    ClpP of Bacillus subtilis is required for competence development, motility, degradative enzyme synthesis, growth at high temperature and sporulation (1998)
    Oxford BSL : Blackwell Science Ltd, UK
    Molecular microbiology 27 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The nucleotide sequence of the Bacillus subtilis clpP gene was determined. The predicted protein shows very high similarity to members of the ClpP family of proteolytic subunits (68% amino acid sequence identity with that of Escherichia coli ). We show that ClpP plays an essential role in stationary phase adaptive responses. Indeed, a ΔclpP mutant was constructed and shown to display a pleiotropic phenotype, including a deficiency in both sporulation initiation and competence for DNA uptake. The ΔclpP mutant has a highly filamentous morphology and appears to be non-motile, as judged by swarm plate assays. Expression of clpP is strongly induced under heat shock conditions, and ClpP is shown to be essential for growth of B. subtilis at high temperature. The role of ClpP in the sporulation and competence regulatory pathways was investigated. ClpP is required for expression of the spoIIA and spoIIG operons, encoding the σF andσE sporulation-specific sigma factors. ClpP is also necessary for the expression of the comK gene, encoding a positive transcriptional regulator of competence genes. ComK-dependent transcription of sacB, encoding the exocellular degradative enzyme levansucrase, was found to be abolished in the ΔclpP mutant. MecA has been characterized previously as a negative regulator of comK expression, whose overproduction inhibits both sporulation and competence development. Expression of a mecA′–′lacZ translational fusion is shown to be increased in the ΔclpP mutant. We suggest that ClpP is involved in controlling MecA levels in the cell through proteolysis. Increased levels of MecA in the absence of ClpP are at least partly responsible for the observed pleiotropic phenotype of the ΔclpP mutant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.00735.x
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  • 9
    Electronic Resource
    Electronic Resource
    ClpE, a novel type of HSP100 ATPase, is part of the CtsR heat shock regulon of Bacillus subtilis (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 32 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Clp ATPases, which include the ubiquitous HSP100 family, are classified according to their structural features and sequence similarities. During the course of the Bacillus subtilis genome sequencing project, we identified a gene encoding a new member of the HSP100 family. We designated this protein ClpE, as it is the prototype of a novel subfamily among the Clp ATPases, and have identified homologues in several bacteria, including Listeria monocytogenes, Enterococcus faecalis, Streptococcus pyogenes, Streptococcus pneumoniae, Lactobacillus sakei and Clostridium acetobutylicum. A unique feature of these Hsp100-type Clp ATPases is their amino-terminal zinc finger motif. Unlike the other class III genes of B. subtilis (clpC and clpP ), clpE does not appear to be required for stress tolerance. Transcriptional analysis revealed two σA-type promoters, expression from which was shown to be inducible by heat shock and puromycin treatment. Investigation of the regulatory mechanism controlling clpE expression indicates that this gene is controlled by CtsR and is thus a member of the class III heat shock genes of B. subtilis. CtsR negatively regulates clpE expression by binding to the promoter region, in which five CtsR binding sites were identified through DNase I footprinting and sequence analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01374.x
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  • 10
    Electronic Resource
    Electronic Resource
    Alternate promoters direct stress-induced transcription of the Bacillus subtilis clpC operon (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 20 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: clpC ofBacillus subtilis is part of an operon containing six genes. Northern blot analysis suggested that all genes are co-transcribed and encode stress-inducible proteins. Two promoters (PA and PB) were mapped upstream of the first gene. PA resembles promoters recognized by the vegetative RNA polymerase EσA. The other promoter (PB) was shown to be dependent on σB, the general stress σ factor in B. subtilis, suggesting that clpC, a potential chaperone, is expressed in a σB-dependent manner. This is the first evidence that σB in B, subtilis is involved in controlling the expression of a gene whose counterpart, clpB, is subject to regulation by σ32 in Escherichia coli, indicating a new function of σB-dependent general stress proteins. PB deviated from the consensus sequence of σB promoters and was only slightly induced by starvation conditions. Nevertheless, strong induction by heat, ethanol, and salt stress occurred at the σB-dependent promoter, whereas the vegetative promoter was only weakly induced under these conditions. However, in a sigB mutant, the σA-like promoter became inducible by heat and ethanol stress, completely compensating for sigB deficiency. Only the downstream σA-like promoter was induced by certain stress conditions such as hydrogen peroxide or puromycin. These results suggest that novel stress-induction mechanisms are acting at a vegetative promoter. Involvement of additional elements in this mode of induction are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1996.tb02511.x
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