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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Gram-positive eubacterium Bacillus subtilis is well known for its high capacity to secrete proteins into the environment. Even though high-level secretion of proteins is an efficient process, it imposes stress on the cell. The present studies were aimed at the identification of systems required to combat this so-called secretion stress. A two-component regulatory system, named CssR–CssS, was identified, which bears resemblance to the CpxR–CpxA system of Escherichia coli. The results show that the CssR/S system is required for the cell to survive the severe secretion stress caused by a combination of high-level production of the α-amylase AmyQ and reduced levels of the extracytoplasmic folding factor PrsA. As shown with a prsA3 mutation, the Css system is required to degrade misfolded exported proteins at the membrane–cell wall interface. This view is supported by the observation that transcription of the htrA gene, encoding a predicted membrane-bound protease of B. subtilis, is strictly controlled by CssS. Notably, CssS represents the first identified sensor for extracytoplasmic protein misfolding in a Gram-positive eubacterium. In conclusion, the results show that quality control systems for extracytoplasmic protein folding are not exclusively present in the periplasm of Gram-negative eubacteria, but also in the Gram-positive cell envelope.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have sequenced and analysed a 3.1 kb fragment of the 55 kb endogenous Bacillus subtilis plasmid pLS20 containing its replication functions. Just outside the region required for autonomous replication, a segment of 18bp was identified as being almost identical to part of the major B. subtilis chromosomal replication terminator. Here, we demonstrate that this segment is part of a functional replication terminator. This newly identified element, designated Ter LS20, is the first replication terminator identified on a theta plasmid from a Gram-positive bacterium. Ter LS20 is distinct from other known replication terminators in the sense that it is functional in both orientations. The region required for bipolar functionality of TerLS20 was delineated to a sequence of 29 bp, which is characterized by an imperfect dyad symmetry.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 10 (1993), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: pWVO2 is a 3.8 kb narrow-host-range plasmid from Lactococcus lactis ssp. cremoris Wg2, which does not replicate in Bacillus subtilis or Escherichia coli. Single-stranded pWVO2 DNA was not observed in lactococcal cells, indicating that this plasmid does not replicate via a rolling-circle mechanism. The sequence of pWVO2 neither showed the structural organization typical for rolling-circle plasmids, nor were sequence similarities with known rolling-circle plasmids present. By 2-D agarose gel electrophoresis of replication intermediates, it was shown that pWVO2 replicates via a theta mechanism. This is the first proof for the existence of theta-replicating plasmids in lactococci. The pWVO2 minimal replicon is strongly related to that of several other lactococcal plasmid replicons. It contains one open reading frame encoding the replication protein, which is preceded by a 22 bp sequence tandemly repeated three and a half times. Further upstream is another 10bp direct repeat present in an A/T-rich sequence. This structural organization resembles that of several iteroncontaining theta-type plasmids from E. coli. Derivatives of pWVO2 were stably maintained in L. lactis and are good candidates for the development of stable food-grade cloning vectors for this organism.
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacillus subtilis contains three chromosomally encoded type I signal peptidases (SipS, SipT and SipU), which remove signal peptides from secretory precursor proteins. In the present study the biological function of SipS and the regulation of its synthesis were analysed. Unlike the type I signal peptidase of Escherichia coli, SipS was essential neither for protein secretion nor viability of the cell. However, in the absence of SipS the rate of processing of several preproteins was reduced, and four of the seven major secreted proteins of B. subtilis were hardly detectable in the growth medium. Surprisingly, the processing of Bacillus amyloliquefaciensα-amylase and the secretion of at least two endogenous B. subtilis proteins was improved in the absence of SipS. These findings indicate that the substrate preference of SipS differs from that of SipT and SipU, and that SipS is an important factor determining the efficiency of protein secretion in B. subtilis. SipS is transcribed in a growth phase- and medium-dependent manner. In minimal medium, the growth phase-dependent transcription of sipS is controlled by the DegS–DegU two-component regulatory system, indicating that the expression of sipS is regulated by the same factors that control the expression of most genes for secreted degradative enzymes. Our observations suggest that B. subtilis can modulate its capacity and specificity for protein secretion through the controlled expression of sipS.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Various strains of Bacillus subtilis (natto) contain small cryptic plasmids that replicate via the rolling-circle mechanism. Like plasmids from other Gram-positive bacteria, these plasmids are composed of several distinct structural modules. A new structural module was identified on the B. subtilis plasmids pTA1015 and pTA1040. It is composed of two genes: one specifies an unidentified protein with a putative signal peptide; and the other (sipP) specifies a functional type I signal peptidase (SPase). The homologous, but non-identical, sipP genes of the two plasmids are the first identified plasmid-specific SPase-encoding genes. With respect to structure and activity, the corresponding enzymes (denoted SipP) are highly similar to the chromosomally encoded SPase, SipS, of B. subtilis and several newly identified SPases of other bacilli. Our findings suggest that plasmid-encoded SPases have evolved because, under certain conditions, SPase can be a limiting factor for protein secretion in B. subtilis.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In Bacillus subtilis competence for genetic transformation develops only in a subpopulation of cells in an isogenic culture. The molecular mechanisms underlying this phenotypic heterogeneity are unknown. In this study, we stepwise simplify the signal transduction cascade leading to competence, yielding a strain devoid of all regulatory inputs for this process that have been identified so far. We demonstrate that auto-stimulation of ComK, the master regulator for competence development, is essential and in itself can be sufficient to generate a bistable expression pattern. We argue that transcriptional regulation determines the threshold of ComK to initiate the auto-stimulatory response, and that the basal level of ComK (in a wild-type strain governed by MecA-mediated proteolytic control) determines the fraction of cells that reach this threshold, and thus develop competence.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd.
    Molecular microbiology 54 (2004), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Activity of the Tat machinery for protein transport across the inner membrane of Escherichia coli and the chloroplast thylakoidal membrane requires the presence of three membrane proteins: TatA, TatB and TatC. Here, we show that the Tat machinery of the Gram-positive bacterium Bacillus subtilis is very different because it contains at least two minimal Tat translocases, each composed of one specific TatA and one specific TatC component. A third, TatB-like component is apparently not required. This implies that TatA proteins of B. subtilis perform the functions of both TatA and TatB of E. coli and thylakoids. Notably, the two B. subtilis translocases named TatAdCd and TatAyCy both function as individual, substrate-specific translocases for the twin-arginine preproteins PhoD and YwbN, respectively. Importantly, these minimal TatAC translocases of B. subtilis are representative for the Tat machinery of the vast majority of Gram-positive bacteria, Streptomycetes being the only known exception with TatABC translocases.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Most bacterial proteins destined to leave the cytoplasm are exported to extracellular compartments or imported into the cytoplasmic membrane via the highly conserved SecA-YEG pathway. In the present studies, the subcellular distributions of core components of this pathway, SecA and SecY, and of the secretory protein pre-AmyQ, were analysed using green fluorescent protein fusions, immunostaining and/or immunogold labelling techniques. It is shown that SecA, SecY and (pre-)AmyQ are located at specific sites near and/or in the cytoplasmic membrane of Bacillus subtilis. The localization patterns of these proteins suggest that the Sec machinery is organized in spiral-like structures along the cell, with most of the translocases organized in specific clusters along these structures. However, this localization appears to be independent of the helicoidal structures formed by the actin-like cytoskeletal proteins, MreB or Mbl. Interestingly, the specific localization of SecA is dynamic, and depends on active translation. Moreover, reducing the phosphatidylglycerol phospholipids content in the bacterial membrane results in delocalization of SecA, suggesting the involvement of membrane phospholipids in the localization process. These data show for the first time that, in contrast to the recently reported uni-ExPortal site in the coccoïd Streptococcus pyogenes, multiple sites dedicated to protein export are present in the cytoplasmic membrane of rod-shaped B. subtilis.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The accumulation of malfolded proteins in the cell envelope of the Gram-positive eubacterium Bacillus subtilis was previously shown to provoke a so-called secretion stress response. In the present studies, proteomic approaches were employed to identify changes in the extracellular proteome of B. subtilis in response to secretion stress. The data shows that, irrespective of the way in which secretion stress is imposed on the cells, the levels of only two extracellular proteins, HtrA and YqxI, display major variations in a parallel manner. Whereas the extracellular level of the HtrA protease is determined through transcriptional regulation, the level of YqxI in the growth medium is determined post-transcriptionally in an HtrA-dependent manner. In the absence of secretion stress, the extracellular levels of HtrA and YqxI are low because of extracytoplasmic proteolysis. Finally, the protease active site of HtrA is dispensable for post-transcriptional YqxI regulation. It is known that Escherichia coli HtrA has combined protease and chaperone-like activities. As this protein shares a high degree of similarity with B. subtilis HtrA, it can be hypothesized that both activities are conserved in B. subtilis HtrA. Thus, a chaperone-like activity of B. subtilis HtrA could be involved in the appearance of YqxI on the extracellular proteome.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 93 (1992), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We studied the segregational stability of plasmids based on pTB913, a 4.5-kb rolling-circle plasmid derived from the thermophilic Bacillus plasmid pTB19. In Bacillus stearothermophilus the stability of pTB913 derivatives appeared to be strain-dependent. In strain CU21 large amounts of single-stranded pTB913 DNA were found and the plasmid was highly unstable at 57°C. In strain NUB3621, however, very low amounts of single-stranded plasmid DNA were formed and pTB913-based replicons were only slightly unstable at 57°C. The NUB3621/pTB913 host-vector system seems appropriate for molecular cloning. A RepA-based replicon, also derived from pTB19 but replicating by a theta mechanism, was highly unstable in B. stearothermophilus NUB3621.
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