This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bischoff, M.
Right arrow Articles by Giachino, P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bischoff, M.
Right arrow Articles by Giachino, P.

 Previous Article  |  Next Article 

Journal of Bacteriology, September 2001, p. 5171-5179, Vol. 183, No. 17
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.17.5171-5179.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Influence of a Functional sigB Operon on the Global Regulators sar and agr in Staphylococcus aureus

M. Bischoff,1,* J. M. Entenza,2 and P. Giachino1

Institute of Medical Microbiology, University of Zürich, CH-8028 Zürich,1 and Division of Infectious Diseases, Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, CH-1011 Lausanne,2 Switzerland

Received 24 January 2001/Accepted 18 June 2001


    ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References

The growth phase-dependent activity profile of the alternate transcription factor sigma B and its effects on the expression of sar and agr were examined in three different Staphylococcus aureus strains by Northern blot analyses and by the use of reporter gene fusion experiments. Significant sigma B activity was detectable only in the clinical isolates MSSA1112 and Newman, carrying the wild-type rsbU allele, but not in the NCTC8325 derivative BB255, which is defective in rsbU. sigma B activity peaked in the late exponential phase and diminished towards the stationary phase when bacteria were grown in Luria-Bertani medium. Transcriptional analysis and a sarP1-sarP2-sarP3 (sarP1-P2-P3)-driven firefly luciferase (luc+) reporter gene fusion demonstrated a strong sigma B activity- and growth phase-dependent increase in sar expression that was totally absent in either rsbU or Delta rsbUVWsigB mutants. In contrast, expression of the agr locus, as measured by RNAIII levels and by an hldp::luc+ fusion, was found to be higher in the absence of sigma B activity, such as in rsbU or Delta rsbUVWsigB mutants, than in wild-type strains. Overexpression of sigma B in BB255 derivatives resulted in a clear increase in sarP1-P2-P3::luc+ expression as well as a strong decrease in hldp::luc+ expression. The data presented here suggest that sigma B increases sar expression while simultaneously reducing the RNAIII level in a growth phase-dependent manner.


    INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References

Staphylococcus aureus is a major human pathogen causing a variety of infections, ranging from minor skin and wound infections to life-threatening diseases (42). Pathogenicity in S. aureus is based on a wide range of cell wall-associated and extracellular proteins that are regulated in a coordinate and growth phase-dependent manner. These virulence determinants are controlled among others by the accessory gene regulator agr and the staphylococcal accessory regulator sar (48). Mutations in either agr or sar result in mutants that are strongly attenuated in virulence compared to their corresponding parental strains (1, 8, 15, 31).

The agr locus regulates the expression of cell wall-associated proteins and secreted exoproteins in response to the density of the bacterial population (37). The proposed function of this regulatory system is to enhance the production of wall-associated adhesins, which interact with the host's matrix proteins, and potential defense factors (protein A) in the early stages of infection. This is followed by the expression of excreted invasion factors, such as hemolysins, proteases, and lipases, that are suggested to be involved in the dissemination of the organism from the primary site of infection once the infection has been established (58). The agr locus comprises two divergent transcriptional units, RNAII and RNAIII, which are transcribed from the agrP2 and agrP3 promoters, respectively (Fig. 1B) (reviewed in reference 46). RNAII encodes a four-gene operon, including a two-component signal transduction system that responds to the concentration of a secreted and processed peptide pheromone, which is encoded within the operon itself. The primary function of the RNAII gene products is to activate the agrP2 and agrP3 promoters, significantly aided by SarA. Transcription from the agrP3 promoter results in a 510-nucleotide RNA molecule (RNAIII), which appears to be the effector molecule of the positive and negative regulation of virulence genes that are controlled by the agr locus (36, 49). RNAIII is thought to regulate most target genes at the level of transcription but has also been shown to influence the translation of some genes (45, 49) and contains a small open reading frame coding for delta hemolysin (hld).


View larger version (21K):
[in this window]
[in a new window]
  		FIG. 1.   Genetic organization of the sar and agr loci of S. aureus. Genetic organization of the sar locus (A) and the agr locus (B) of S. aureus and schematic representation of the integration of sarP1-P2-P3::luc+ or hldp::luc+ fusion constructs into the S. aureus chromosome by single crossover. For a description of construction of the plasmids pECsarP1-P2-P3-luc+ and pEChldp-luc+ and integration of the constructs into the S. aureus chromosome, see Materials and Methods. Open reading frames, promoters, and respective transcripts are indicated.

SarA, the major functional protein encoded by the sar locus, is generally believed to be required for the activation of expression of the agr locus (20, 21, 46) and influences the regulation of several virulence factors independently from agr (7, 11, 14, 19, 41, 60). SarA is essentially involved in the capacity of S. aureus to survive inside of polymorphonuclear neutrophils (33), and the ability of S. aureus to enter mammalian cells and induce apoptosis is supposed to be dependent on factors regulated by sar and agr (58). SarA expression itself is controlled by three different, tandemly arranged promoters (Fig. 1A) in a growth phase-dependent manner (3, 23, 43). Although one of these transcripts, sarC, was shown to be controlled by the alternative transcription factor sigma B in vitro (10, 28, 43), the inadvertant use of an rsbU mutant to compare sar expression in a sigB mutant may have wrongly suggested that sigma B was involved neither in the transcriptional control of the sar locus nor in agr expression (12, 14, 17). The strains used in those studies were recently shown to possess almost no sigma B activity due to a mutation in the rsbU gene, which encodes a positive regulator of sigma B (30). The transcription factor sigma B itself, organized in the rsbUVWsigB operon, is supposed to be activated by a cascade encompassing RsbU, an RsbV-specific phosphatase, the anti-anti-sigma factor RsbV, and the anti-sigma factor RsbW.

In this study we demonstrate by the use of transcriptional analyses and reporter gene fusion experiments in three different genetic backgrounds that transcription of both the sar and agr loci are clearly influenced by the sigma B activity in S. aureus strains harboring a functional sigB operon.


    MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References

Bacterial strains, plasmids, and culture conditions. The bacterial strains and plasmids used in this study are listed in Table 1. S. aureus was routinely grown in Luria-Bertani (LB) medium at 37°C and at 200 rpm. Antibiotics were used at the following concentrations: for erythromycin and tetracycline, 10 µg ml-1; for ampicillin, 50 µg ml-1.

                              
View this table:
[in this window]
[in a new window]
  		TABLE 1.   Strains and plasmids used in this study

General methods. All DNA manipulations, basic molecular methods, and handling of Escherichia coli were performed in accordance with standard protocols (54). Genetic manipulation of S. aureus was done as described earlier (39). The general transducing phage 80alpha was used for transductions.

Construction of pECsarP1-P2-P3-luc+ and pEChldp-luc+. A DNA fragment covering 867 bp of the sar promoter region of S. aureus RN4220 was generated by PCR using an upstream primer (5'-CGGTACCGTTGATTTGGGTAGTATGC-3') including a KpnI linker (underlined) and a downstream primer (5'-TTGCCATGGTTAAAACCTCCC-3') including a NcoI site (underlined), with italic nucleotides corresponding to positions 5 to 24 and 852 to 872 of the sequence found under GenBank accession no. U46541, respectively. For hldp::luc+, a DNA fragment covering 1 kb of the agr locus of S. aureus RN4220 was generated by PCR using an upstream primer (5'-GTGCCATGGAAATCACTCCTTCC-3') including a NcoI site (underlined) and a downstream primer (5'-TGGTACCTCAACTTCATCCATTATG-3') including a KpnI site (underlined), with italic nucleotides corresponding to positions 397 to 419 and 1348 to 1372 of the sequence found under GenBank accession no. AF230358, respectively. The PCR products obtained were digested with KpnI and NcoI and cloned in frame with the 5' end of the luciferase gene of plasmid pSP-luc+. Sequence analysis and comparison confirmed the identity of the constructs to the RN6390 sequence or RN4220 sequence, respectively. A 2.5-kb KpnI-EcoRI fragment, including the sar promoter region fused to the luciferase coding region, or a 2.6-kb KpnI-EcoRI fragment, including the hld promoter region fused to the luciferase coding region, was subsequently cloned into the suicide plasmid pEC1 (9) to obtain the plasmids pECsarP1-P2-P3-luc+ (Fig. 1A) and pEChldp-luc+ (Fig. 1B), respectively. The plasmids obtained were transformed by electroporation into RN4220 and transduced into different S. aureus genetic backgrounds.

Northern blot analyses. Isolation of total RNA was done as described by Cheung et al. (16). Eight micrograms of total RNA of each sample was electrophoresed through a 1.5% agarose-0.66 M formaldehyde gel in morpholinepropanesulfonic acid running buffer (20 mM morpholinepropanesulfonic acid, 10 mM sodium acetate, 2 mM EDTA [pH 7]). Blotting of RNA onto a positively charged nylon membrane (Roche, Basel, Switzerland) was performed with a vacuum blotter (Pharmacia, Uppsala, Sweden). The intensities of the 23S and 16S rRNA bands stained with ethidium bromide were verified to be equivalent in all the samples before transfer. Labeling and hybridization were done by the use of the digoxigenin labeling and detection kits according to the manufacturer's instructions (Roche). The following specific primers were used to generate the digoxigenin-labeled DNA probes by PCR labeling: SasarA+, 5'-AGGGAGGTTTTAAACATGGC-3'; SasarA-, 5'-CTCGACTCAATAATGATTCG-3' (nucleotides 851 to 870 and 1177 to 1196 of the sequence found under GenBank accession no. U46541); RNAIII+, 5'-GTGATGGAAAATAGTTGATGAG-3'; RNAIII-, 5'-GTGAATTTGTTCACTGTGTCG-3' (nucleotides 453 to 474 and 333 to 353 of the sequence under GenBank accession no. AF230358).

Luciferase assay. Bacterial cells from overnight cultures containing the appropriate antibiotic were diluted with fresh LB medium to an optical density at 600 nm (OD600) of 0.01. Freshly diluted cells were incubated without antibiotics at 37°C and at 200 rpm. S. aureus cells, obtained at different growth stages, were harvested by centrifugation at 11,000 × g during 1 min at room temperature, and the cell pellets were resuspended in phosphate-buffered saline (PBS) (137 mM NaCl, 2.7 mM KCl, 4.3 mM Na2HPO4, 1.4 mM KH2PO4 [pH 7.3]) to an OD600 of 10. Luciferase activity was that determined by rapidly mixing PBS-resuspended cells (10 µl) with an equal volume of Luciferase Assay Substrate (Promega, Madison, Wis.). Luminescence was measured on a Turner Designs TD-20/20 Luminometer (Promega) for a time period of 10 s with a delay of 2 s.

Fibronectin binding assay. Binding of S. aureus to fibronectin was measured quantitatively in microtiter plates, by a slight modification of a previously described method (44). Briefly, 50 µl of human fibronectin (Sigma, Buchs, Switzerland) was serially diluted twofold from a starting concentration of 500 µg/ml in PBS. Bacterial cells grown to exponential or stationary phase were harvested by centrifugation and washed in PBS, and 20 µl of a suspension (5 × 108 CFU) was added to the fibronectin dilutions. The lowest concentration of fibronectin triggering clumping after overnight incubation at 4°C was recorded as the titer.


    RESULTS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References

sigma B activity in S. aureus. The sigma B activities of the two genetically distinct strains Newman and MSSA1112 and their respective Delta rsbUVWsigB mutants, as well as those of the rsbU strain BB255 and its derivative GP268, transformed with the rsbU wild-type allele, were analyzed during growth by the use of the asp23 reporter gene system (30). The two clinical isolates MSSA1112 and Newman possessed quite similar sigma B activity profiles in LB medium, with a maximal sigma B activity in late exponential growth phase followed by a significant decrease thereafter (Fig. 2B and C). The sigma B activity profile obtained for strain GP268 (MB49) was comparable to those found for strains MSSA1112 (MB73) and Newman (MB32), while its parental strain produced almost no sigma B activity throughout the whole growth cycle (Fig. 2A). Additionally, all three Delta rsbUVWsigB mutants were unable to produce any sigma B-dependent activity at all. The unexpected strong decrease in sigma B activity that was observed from the onset of stationary phase was confirmed by monitoring the transcription of the sigma B-dependent genes asp23 and sigB in Northern blot analyses. Both transcripts were found to be the most abundant during late exponential growth phase, and their levels were drastically reduced during stationary phase (data not shown).


View larger version (18K):
[in this window]
[in a new window]
  		FIG. 2.   sigma B activity during growth of S. aureus. Expression of asp23::luc+ during growth of S. aureus strains BB255 (A), MSSA1112 (B), Newman (C), and their respective sigB mutants. Strains were grown in LB medium at 37°C. Bacterial growth was measured as the OD600 (solid symbols). sigma B transcriptional activity was determined by measuring the luciferase activity of Luc+ (open symbols), the product of the luc+ reporter gene fused to the sigma B-dependent promoters of asp23 (asp23p). (A) Squares, S. aureus strain MB33 (BB255, asp23p::luc+); triangles, strain MB49 (BB255, rsbU+ asp23p::luc+); circles, strain MB90 (BB255, Delta rsbUVWsigB asp23p::luc+). (B) Squares, S. aureus strain MB73 (MSSA1112, asp23p::luc+); circles, strain MB70 (MSSA1112, Delta rsbUVWsigB asp23p::luc+). (C) Squares, S. aureus strain MB32 (Newman, asp23p::luc+); circles, strain MB69 (Newman, Delta rsbUVWsigB asp23p::luc+).

Influence of sigma B on the expression of the sar locus. Northern blot analyses with the sarA gene as a probe showed strong sarA transcription, originating from the sigma A-dependent sarP1 promoter, during exponential growth (OD600, 0.3 to 1.5) and declining with the onset of stationary phase in all strains analyzed (Fig. 3). A similar time course but much weaker transcription was observed in all strains for sarB, originating from the sigma A-dependent sarP2 promoter. In contrast, sigma B-dependent transcription of sarC from the sarP3 promoter was detectable only in the wild-type strains MSSA1112 and Newman, not in BB255 or any of the Delta rsbUVWsigB mutants. sarC-specific transcripts were detectable abundantly from late exponential growth phase up to stationary phase (OD600, 1.5 to 5.0). Reporter gene fusion experiments with the luciferase gene luc+ fused to the sarP1, sarP2, and sarP3 (sarP1-P2-P3) promoters suggested an increased SarA production in strains MSSA1112 and Newman with the beginning of late exponential growth phase that paralleled the time course of the overall sar transcripts observed in those strains. No such increase in luciferase activity was detectable with the rsbU mutant BB255 (Fig. 4A) or in any of the Delta rsbUVWsigB mutants. Plasmid pIK64 (Pxyl::sigB)-mediated xylose-induced overexpression of sigma B in the BB255 derivative MB98 resulted in a strong increase in sarP1-P2-P3::luc+ expression (Fig. 5A), which was not observed with the control plasmid pTX15 (Fig. 5B), unambiguously proving sigma B to influence sar expression directly or indirectly.


View larger version (49K):
[in this window]
[in a new window]
  		FIG. 3.   Northern blot analyses of the sar locus. Total RNAs (8 µg/lane) of S. aureus strains BB255 (A), MSSA1112 (B), Newman (C), and their respective sigB mutants were blotted onto positively charged nylon membranes and subjected to Northern blot analyses. RNAs were obtained from cells grown in LB medium at 37°C and harvested at different growth stages (indicated as OD600 values [numbers above the lanes]). The blotted membranes were hybridized using a digoxigenin-labeled DNA probe specific for sarA (for details on the construction, see Materials and Methods). The RNA molecular weight marker I (Roche) was used as a size marker. Relevant transcript signals are indicated.


View larger version (17K):
[in this window]
[in a new window]
  		FIG. 4.   Role of sigma B in the regulation of sarP1-P2-P3::luc+ expression during growth. S. aureus derivatives of strains BB255 (A), MSSA 1112 (B), Newman (C), and their respective sigB mutants were grown in LB medium at 37°C. Bacterial growth was measured by OD600 (closed symbols). sarP1-P2-P3::luc+ expression was determined by measuring the luciferase activity of the reporter gene luc+ (open symbols). (A) Squares, S. aureus strain MB98 (BB255, sarP1-P2-P3::luc+); circles, strain MB102 (BB255, sigB sarP1-P2-P3::luc+). (B) Squares, S. aureus strain MB105 (MSSA1112, sarP1-P2-P3::luc+); circles, strain MB113 (MSSA1112, sigB sarP1-P2-P3::luc+). (C) Squares, S. aureus strain MB100 (Newman, sarP1-P2-P3::luc+); circles, strain MB101 (Newman, sigB sarP1-P2-P3::luc+).


View larger version (16K):
[in this window]
[in a new window]
  		FIG. 5.   Effect of overexpressed sigma B on the expression of sarP1-P2-P3::luc+. S. aureus derivatives of strain MB98 (BB255, sarP1-P2-P3::luc+), harboring plasmid pIK64 (Pxyl::sigB) (A) or control plasmid pTX15 (Pxyl) (B) were grown in LB medium at 37°C. Growth was measured as the OD600 (closed symbols). Growing cultures were split into equal parts at the OD600 of 1, and overexpression of sigma B was induced in one of the parts by supplementing 0.5% xylose (diamonds), while the control part was left without addition (squares). The arrow denotes the time point of supplementation. sarP1-P2-P3::luc+ expression (open symbols) was determined by measuring the luciferase activity of the reporter gene luc+ as described in Materials and Methods.

Influence of sigma B on the expression of the agr locus. Comparison of the growth phase-dependent transcription of RNAIII in Northern blot analyses revealed low transcription levels and a delayed induction of RNAIII expression in the wild-type strains MSSA1112 and Newman compared to results for their corresponding Delta rsbUVWsigB mutants (Fig. 6B and C). The RNAIII expression profile of strain GP268 (BB255 rsbU+) paralleled the transcription profiles found for strains MSSA1112 and Newman, with expression being significantly delayed and at a lower level than that for BB255 (Fig. 6A). Reporter gene fusion experiments, using the luciferase gene luc+ fused to the hld gene, carried by RNAIII (Fig. 1B), confirmed these data. The RNAIII-representing luciferase activity profiles of strains carrying the wild-type rsbU allele were significantly lower than those for Delta rsbUVWsigB mutants and BB255, respectively (Fig. 7). Overexpression of sigma B in the BB255 derivative MB95, harboring plasmid pIK64, resulted in a strong decrease in hldp::luc+ expression from that of the control (Fig. 8), corroborating the negative regulatory effect of sigma B on agr expression.


View larger version (39K):
[in this window]
[in a new window]
  		FIG. 6.   Northern blot analyses of RNAIII. Total RNAs (8 µg/lane) of S. aureus strains BB255 and GP268 (BB255, rsbU+) (A), MSSA1112 and MB39 (MSSA1112, Delta rsbUVWsigB) (B), and Newman and IK 184 (Newman, Delta rsbUVWsigB) (C) were blotted onto positively charged nylon membranes and subjected to Northern blot analyses. RNAs were obtained from cells grown in LB medium at 37°C and harvested at different growth stages (indicated as OD600 values above the lanes). The blotted membranes were hybridized using a digoxigenin-labeled DNA probe specific for RNAIII (for details on construction, see Materials and Methods). The RNA molecular weight marker I (Roche) was used as the size marker. Relevant transcript signals are indicated.


View larger version (18K):
[in this window]
[in a new window]
  		FIG. 7.   Role of sigma B in the regulation of hldP::luc+ expression during growth. S. aureus derivatives of strains BB255 (A), MSSA1112 (B), and Newman (C) were grown in LB medium at 37°C. Bacterial growth was measured by OD600 (closed symbols). hldp::luc+ expression was determined by measuring the luciferase activity of the reporter gene luc+ (open symbols) as described in Materials and Methods. (A) Squares, S. aureus strain MB95 (BB255, hldp::luc+); diamonds, strain MB94 (BB255, rsbU+ hldp::luc+). (B) Squares, S. aureus strain MB104 (MSSA1112, hldp::luc+); circles, strain MB112 (MSSA1112, sigB hldp::luc+). (C) Squares, S. aureus strain MB97 (Newman, hldp::luc+); circles, strain MB103 (Newman, sigB hldp::luc+).


View larger version (17K):
[in this window]
[in a new window]
  		FIG. 8.   Effect of overexpressed sigma B on the expression of hldP::luc+. S. aureus derivatives of strain MB95 (BB255 hldp::luc+), harboring plasmid pIK64 (Pxyl::sigB) (A) or control plasmid pTX15 (Pxyl) (B), were grown in LB medium at 37°C. Growth was measured as the OD600 (closed symbols). Growing cultures were split into equal parts at the OD600 of 1, and overexpression of sigma B was induced in one of the parts by supplementing 0.5% xylose (diamonds), while the control part was left without addition (squares). The arrow denotes the time point of supplementation. hldp::luc+ expression (open symbols) was determined by measuring the luciferase activity of the reporter gene luc+ as described in Materials and Methods.

Fibronectin binding activity. Since sar and agr are known to influence the ability of S. aureus to bind to fibronectin (55, 60), the effects of RsbU on the fibronectin binding capacity were determined with strain BB255 and its derivatives (Table 2). Strain GP268, carrying an intact sigB operon, showed a more than 100-fold-lower fibronectin-clumping titer than its rsbU-defective parent, BB255, irrespective of the growth phase, while no difference was apparent between BB255 and its Delta rsbUVWsigB mutant.

                              
View this table:
[in this window]
[in a new window]
  		TABLE 2.   Titration of fibronectin clumping of S. aureus


    DISCUSSION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References

Most of our knowledge of the regulation of sigma B in S. aureus has been adapted from the well-characterized sigma B regulon of the closely related soil bacterium Bacillus subtilis (reviewed in reference 34). In this organism, sigma B has been shown to function as a stress- and stationary phase-specific transcription factor. In B. subtilis, activation of sigma B appears to be basically dependent on the activity of the two RsbV-specific phosphatases, RsbU and RsbP, with the latter being essential for the stationary phase and energy stress-dependent activation of sigma B (56). RsbU was found to be of importance only for the environmental stress activation of this sigma factor (57, 59, 61). The data presented here and elsewhere (6, 30) instead suggest sigma B of S. aureus to be a transcription factor with the main activity in late exponential growth phase rather than in stationary phase. Additionally, the data clearly demonstrated that the natural rsbU mutant BB255 was almost completely unable to express sigma B activity, illustrating the importance of RsbU for the overall activity level of sigma B in S. aureus. Accidentally, nearly all studies of the influence of sigma B on the expression of sar and agr have been carried out with NCTC8325 isogenic backgrounds, harboring the mutation in rsbU (12, 14, 23, 43). In consequence, the findings presented here call into question the sigma B-dependent results obtained from such strains.

Transcriptional data and reporter gene fusions of the sar locus revealed a strong sigma B-dependent transcription of sarC in S. aureus strains harboring an intact sigB operon, while no such transcription was detectable in the rsbU-deficient strain BB255 nor in any of the Delta rsbUVWsigB mutants (Fig. 3 and 4). This results are in contrast to the findings of Bayer et al. (3) and Manna et al. (43), who detected significant amounts of sarC transcripts during late exponential phase in the closely related rsbU-deficient strain RN6390. It is noteworthy that the reporter gene fusion experiments of Manna et al. (43) performed with strain RN6390 revealed only little activity for the sarP3 promoter, the level of which was approximately 50-fold lower than that for the sarP1 promoter. Interestingly, the maximum activity obtained in this study for the sarP3 promoter was comparable to that found for the sarP2 promoter. A comparison of the reporter gene data obtained from Manna et al. (43) with the intensities of the different sar transcripts presented here in Fig. 3 led us to the conclusion that the RN6390 strain used by Manna et al. also possessed almost no sigma B activity. This conclusion is further strengthened by the findings of Cheung et al. (17), who reported neither in vitro nor in vivo activity of the sarP3 promoter in strain RN6390, in accordance with our finding that the luciferase activity profile of BB255 was indistinguishable from that of its Delta rsbUVWsigB mutant. Both findings fit well with our deduction that normal levels of sigma B-dependent transcription of sarC occur only in the presence of a functional RsbU phosphatase. Our data demonstrate that expression of the sar locus is significantly upregulated by sigma B in a growth phase-dependent manner in S. aureus strains harboring an intact sigB operon. Thus, we postulate that sigma B positively contributes to the overall level of SarA in S. aureus. This hypothesis is strengthened by recent findings of Gertz et al. (29), who reported significantly lower SarA levels in a Delta rsbUVWsigB mutant of the rsbU+ strain COL.

The influence of SarA on the expression of the agr locus has been the topic of several studies (13, 20, 21, 35, 46, 53). Even though a factor(s) other than SarA (e.g., ORF3, RAP, and RIP) is suggested to participate in controlling agr-related transcription (2, 13, 20, 21), SarA is currently believed to stimulate the expression from both the agrP2 and agrP3 promoters, leading ultimately to the upregulation of RNAIII (21; for a review, see reference 48). The sigma B-dependent upregulation of sar expression observed in rsbU+ strains would be expected therefore to result in an increase in agr expression. However, the data presented here revealed a weaker RNAIII transcription for the rsbU+ strains MSSA1112 and Newman than for their Delta rsbUVWsigB mutants, suggesting that agr expression is negatively influenced by sigma B activity, irrespective of the positive effect of sigma B on sar expression. This finding is supported by a recent study of Chakrabarti and Misra (10), demonstrating an inhibitory influence of SarA on transcription from both the agrP2 and agrP3 promoters in vitro. The authors suggest that either SarA, together with an as-yet-uncharacterized cellular factor(s), activates transcription of the agr operon, or SarA regulates expression of one or more factors which then activate agr expression. In line with this hypothesis, this as-yet-uncharacterized cellular factor(s) involved in the activation of agr expression may be positively regulated by SarA but dominated negatively by sigma B activity.

Many potential virulence factors have been shown to be regulated by SarA and RNAIII in a cooperative way (11, 13, 18, 27, 52), but the expression of several virulence factors was found to be upregulated by one regulator but repressed by the other (55, 60). Additionally, some virulence factors are influenced by one of the two loci but unaffected by the other one (7, 26, 32). Thus, the sigma B-mediated increase in SarA, accompanied by the decrease in RNAIII, is very likely to enhance these phenomena, resulting in severe growth phase-dependent differences in the expression profiles of some virulence factors. One possible role of sigma B in this scenario is to prolong the production of cell surface proteins, such as fibronectin binding proteins, that are positively influenced by SarA and negatively influenced by agr (55, 60). Simultaneously, sigma B may down-regulate RNAIII-specific activities, i.e., the repression of protein A and upregulation of exoproteins (36, 49) or the production of capsular polysaccharides (22, 51). Consistent with this hypothesis is our finding that the rsbU+ derivative GP268 possessed a significantly lower fibronectin-clumping titer than its rsbU-defective parent, BB255, signalling the presence of larger quantities of fibronectin binding proteins in GP268 than in BB255.

The impact of either SarA and/or RNAIII on the expression of virulence factors in S. aureus is well documented. On account of the studies performed with NCTC8325 derivatives, it is unquestionable that sigB mutants are still able to produce sufficient amounts of those two global regulators to be virulent, which led to the conclusion that sigma B has no essential function in the virulence and pathogenicity of S. aureus (12). This conclusion is further strengthened by the findings of Nicholas et al. (47), who observed no differences between the clinical isolate WCUH29 and its isogenic Delta sigB mutant in their ability to cause infections in three distinct animal infection models. However, we agree with Gertz et al. (29), who question whether the infection models analyzed so far really reflect the natural situation in the host. The findings that both agr and sar expression are significantly influenced by sigma B in an rsbU+ genetic background should be reason to reevaluate if and how sigma B is involved in the virulence and pathogenicity of S. aureus.


    ACKNOWLEDGMENTS

We are grateful to B. Berger-Bächi for critically reading and commenting on the manuscript. Preliminary sequence data was obtained from The Institute of Genomic Research (TIGR) through the website at http://www.tigr.org. Sequencing of Staphylococcus aureus COL was accomplished with support from National Institute of Allergy and Infectious Diseases (NIAID) and the Merck Genome Research Institute (MGRI).

This work was supported by the Swiss National Science Foundation grant NF 31-46762.96 to F. H. Kayser.


    FOOTNOTES

* Corresponding author. Mailing address: Institute of Medical Microbiology, University of Zürich, Gloriastr. 32, Postfach, CH-8028 Zürich, Switzerland. Phone: 41 1 634 26 70. Fax: 41 1 634 49 06. E-mail: bischoff{at}immv.unizh.ch.


    REFERENCES
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References

1. Abdelnour, A., S. Arvidson, T. Bremell, C. Ryden, and A. Tarkowski. 1993. The accessory gene regulator (agr) controls Staphylococcus aureus virulence in a murine arthritis model. Infect. Immun. 61:3879-3885[Abstract/Free Full Text].
2. Balaban, N., T. Goldkorn, R. T. Nhan, L. B. Dang, S. Scott, R. M. Ridgley, A. Rasooly, S. C. Wright, J. W. Larrick, R. Rasooly, and J. R. Carlson. 1998. Autoinducer of virulence as a target for vaccine and therapy against Staphylococcus aureus. Science 280:438-440[Abstract/Free Full Text].
3. Bayer, M. G., J. H. Heinrichs, and A. L. Cheung. 1996. The molecular architecture of the sar locus in Staphylococcus aureus. J. Bacteriol. 178:4563-4570[Abstract/Free Full Text].
4. Berger-Bächi, B. 1983. Increase in transduction efficiency of Tn551 mediated by the methicillin resistance marker. J. Bacteriol. 154:533-535[Abstract/Free Full Text].
5. Bischoff, M., M. Roos, J. Putnik, A. Wada, P. Glanzmann, P. Giachino, P. Vaudaux, and B. Berger-Bächi. 2001. Involvement of multiple genetic loci in Staphylococcus aureus teicoplanin resistance. FEMS Microbiol. Lett. 194:77-82[CrossRef][Medline].
6. Bischoff, M., and B. Berger-Bächi. 2001. Teicoplanin stress-selected mutations increasing sigma B activity in Staphylococcus aureus. Antimicrob. Agents Chemother. 45:1714-1720[Abstract/Free Full Text].
7. Blevins, J. S., A. F. Gillaspy, T. M. Rechtin, B. K. Hurlburt, and M. S. Smeltzer. 1999. The staphylococcal accessory regulator (sar) represses transcription of the Staphylococcus aureus collagen adhesin gene (cna) in an agr-independent manner. Mol. Microbiol. 33:317-326[CrossRef][Medline].
8. Booth, M. C., A. L. Cheung, K. L. Hatter, B. D. Jett, M. C. Callegan, and M. S. Gilmore. 1997. Staphylococcal accessory regulator (sar) in conjunction with agr contributes to Staphylococcus aureus virulence in endophthalmitis. Infect. Immun. 65:1550-1556[Abstract].
9. Brücker, R. 1997. Gene replacement in Staphylococcus carnosus and Staphylococcus xylosus. FEMS Microbiol. Lett. 151:1-8[Medline].
10. Chakrabarti, S. K., and T. K. Misra. 2000. SarA represses agr operon expression in a purified in vitro Staphylococcus aureus transcription system. J. Bacteriol. 182:5893-5897[Abstract/Free Full Text].
11. Chan, P. F., and S. J. Foster. 1998. Role of SarA in virulence determinant production and environmental signal transduction in Staphylococcus aureus. J. Bacteriol. 180:6232-6241[Abstract/Free Full Text].
12. Chan, P. F., S. J. Foster, E. Ingham, and M. O. Clements. 1998. The Staphylococcus aureus alternative sigma factor sigma B controls the environmental stress response but not starvation survival or pathogenicity in a mouse abscess model. J. Bacteriol. 180:6082-6089[Abstract/Free Full Text].
13. Cheung, A. L., M. G. Bayer, and J. H. Heinrichs. 1997. sar genetic determinants necessary for transcription of RNAII and RNAIII in the agr locus of Staphylococcus aureus. J. Bacteriol. 179:3963-3971[Abstract/Free Full Text].
14. Cheung, A. L., Y. T. Chien, and A. S. Bayer. 1999. Hyperproduction of alpha-hemolysin in a sigB mutant is associated with elevated SarA expression in Staphylococcus aureus. Infect. Immun. 67:1331-1337[Abstract/Free Full Text].
15. Cheung, A. L., K. J. Eberhardt, E. Chung, M. R. Yeaman, P. M. Sullam, M. Ramos, and A. S. Bayer. 1994. Diminished virulence of a sar-agr- mutant of Staphylococcus aureus in the rabbit model of endocarditis. J. Clin. Investig. 94:1815-1822.
16. Cheung, A. L., K. J. Eberhardt, and V. A. Fischetti. 1994. A method to isolate RNA from gram-positive bacteria and mycobacteria. Anal. Biochem. 222:511-514[CrossRef][Medline].
17. Cheung, A. L., C. C. Nast, and A. S. Bayer. 1998. Selective activation of sar promoters with the use of green fluorescent protein transcriptional fusions as the detection system in the rabbit endocarditis model. Infect. Immun. 66:5988-5993[Abstract/Free Full Text].
18. Cheung, A. L., and P. Ying. 1994. Regulation of alpha- and beta-hemolysins by the sar locus of Staphylococcus aureus. J. Bacteriol. 176:580-585[Abstract/Free Full Text].
19. Chien, Y., A. C. Manna, S. J. Projan, and A. L. Cheung. 1999. SarA, a global regulator of virulence determinants in Staphylococcus aureus, binds to a conserved motif essential for sar-dependent gene regulation. J. Biol. Chem. 274:37169-37176[Abstract/Free Full Text].
20. Chien, Y. T., and A. L. Cheung. 1998. Molecular interactions between two global regulators, sar and agr, in Staphylococcus aureus. J. Biol. Chem. 273:2645-2652[Abstract/Free Full Text].
21. Chien, Y. T., A. C. Manna, and A. L. Cheung. 1998. SarA level is a determinant of agr activation in Staphylococcus aureus. Mol. Microbiol. 30:991-1001[CrossRef][Medline].
22. Dassy, B., T. Hogan, T. J. Foster, and J. M. Fournier. 1993. Involvement of the accessory gene regulator (agr) in expression of type 5 capsular polysaccharide. J. Gen. Microbiol. 139:1301-1306.
23. Deora, R., T. Tseng, and T. K. Misra. 1997. Alternative transcription factor sigma SB of Staphylococcus aureus: characterization and role in transcription of the global regulatory locus sar. J. Bacteriol. 179:6355-6359[Abstract/Free Full Text].
24. Duthie, E. S., and L. L. Lorenz. 1952. Staphylococcal coagulase: mode of action and antigenicity. J. Gen. Microbiol. 6:95-107[Abstract/Free Full Text].
25. Entenza, J. M., J. Vouillamoz, M. P. Glauser, and P. Moreillon. 1997. Levofloxacin versus ciprofloxacin, flucloxacillin, or vancomycin for treatment of experimental endocarditis due to methicillin-susceptible or -resistant Staphylococcus aureus. Antimicrob. Agents Chemother. 41:1662-1667[Abstract].
26. Fujimoto, D. F., and K. W. Bayles. 1998. Opposing roles of the Staphylococcus aureus virulence regulators, Agr and Sar, in Triton X-100- and penicillin-induced autolysis. J. Bacteriol. 180:3724-3726[Abstract/Free Full Text].
27. Fujimoto, D. F., E. W. Brunskill, and K. W. Bayles. 2000. Analysis of genetic elements controlling Staphylococcus aureus lrgAB expression: potential role of DNA topology in SarA regulation. J. Bacteriol. 182:4822-4828[Abstract/Free Full Text].
28. Gertz, S., S. Engelmann, R. Schmid, K. Ohlsen, J. Hacker, and M. Hecker. 2000. Regulation of sigmaB-dependent transcription of sigB and asp23 in two different Staphylococcus aureus strains. Mol. Gen. Genet. 261:558-566.
29. Gertz, S., S. Engelmann, R. Schmid, A.-K. Ziebandt, K. Tischer, C. Scharf, J. Hacker, and M. Hecker. 2000. Characterization of the sigma B regulon in Staphylococcus aureus. J. Bacteriol. 182:6983-6991[Abstract/Free Full Text].
30. Giachino, P., S. Engelmann, and M. Bischoff. 2001. sigma B activity depends on RsbU in Staphylococcus aureus. J. Bacteriol. 183:1843-1852[Abstract/Free Full Text].
31. Gillaspy, A. F., S. G. Hickmon, R. A. Skinner, J. R. Thomas, C. L. Nelson, and M. S. Smeltzer. 1995. Role of the accessory gene regulator (agr) in pathogenesis of staphylococcal osteomyelitis. Infect. Immun. 63:3373-3380[Abstract].
32. Gillaspy, A. F., J. M. Patti, F. L. J. Pratt, J. J. Iandolo, and M. S. Smeltzer. 1997. The Staphylococcus aureus collagen adhesin-encoding gene (cna) is within a discrete genetic element. Gene 96:239-248.
33. Gresham, H. D., J. H. Lowrance, T. E. Caver, B. S. Wilson, A. L. Cheung, and F. P. Lindberg. 2000. Survival of Staphylococcus aureus inside neutrophils contributes to infection. J. Immunol. 164:3713-3722[Abstract/Free Full Text].
34. Hecker, M., and U. Völker. 1998. Non-specific, general and multiple stress resistance of growth-restricted Bacillus subtilis cells by the expression of the sigmaB regulon. Mol. Microbiol. 29:1129-1136[CrossRef][Medline].
35. Heinrichs, J. H., M. G. Bayer, and A. L. Cheung. 1996. Characterization of the sar locus and its interaction with agr in Staphylococcus aureus. J. Bacteriol. 178:418-423[Abstract/Free Full Text].
36. Janzon, L., and S. Arvidson. 1990. The role of the delta-lysin gene (hld) in the regulation of virulence genes by the accessory gene regulator (agr) in Staphylococcus aureus. EMBO J. 9:1391-1399[Medline].
37. Ji, G., R. C. Beavis, and R. P. Novick. 1995. Cell density control of staphylococcal virulence mediated by an octapeptide pheromone. Proc. Natl. Acad. Sci. USA 92:12055-12059[Abstract/Free Full Text].
38. Kreiswirth, B. N., S. Löfdahl, M. J. Bentley, M. O'Reilly, P. M. Schlievert, M. S. Bergdoll, and R. P. Novick. 1983. The toxic shock syndrome exotoxin structural gene is not detectable transmitted by a prophage. Nature 305:680-685.
39. Kullik, I., and P. Giachino. 1997. The alternative sigma factor sigB in Staphylococcus aureus: regulation of the sigB operon in response to growth phase and heat shock. Arch. Microbiol. 167:151-159[CrossRef][Medline].
40. Kullik, I., P. Giachino, and T. Fuchs. 1998. Deletion of the alternative sigma factor sigma B in Staphylococcus aureus reveals its function as a global regulator of virulence genes. J. Bacteriol. 180:4814-4820[Abstract/Free Full Text].
41. Lindsay, J. A., and S. J. Foster. 1999. Interactive regulatory pathways control virulence determinant production and stability in response to environmental conditions in Staphylococcus aureus. Mol. Gen. Genet. 262:323-331[CrossRef][Medline].
42. Lowy, F. 1998. Staphylococcus aureus infections. N. Engl. J. Med. 339:520-532[Free Full Text].
43. Manna, A. C., M. G. Bayer, and A. L. Cheung. 1998. Transcriptional analysis of different promoters in the sar locus in Staphylococcus aureus. J. Bacteriol. 180:3828-3836[Abstract/Free Full Text].
44. McDevitt, D., P. Vaudaux, and T. J. Foster. 1992. Genetic evidence that bound coagulase of Staphylococcus aureus is not clumping factor. Infect. Immun. 60:1514-1523[Abstract/Free Full Text].
45. Morfeldt, E., D. Taylor, A. von Gabain, and S. Arvidson. 1995. Activation of alpha-toxin translation in Staphylococcus aureus by the trans-encoded antisense RNA, RNAIII. EMBO J. 15:4569-4577.
46. Morfeldt, E., K. Tegmark, and S. Arvidson. 1996. Transcriptional control of the agr-dependent virulence gene regulator, RNAIII, in Staphylococcus aureus. Mol. Microbiol. 21:1227-1237[CrossRef][Medline].
47. Nicholas, R. O., T. Li, D. McDevitt, A. Marra, S. Sucoloski, P. L. Demarsh, and D. R. Gentry. 1999. Isolation and characterization of a sigB deletion mutant of Staphylococcus aureus. Infect. Immun. 67:3667-3669[Abstract/Free Full Text].
48. Novick, R. P. 2000. Pathogenicity factors and their regulation, p. 392-407. In V. A. Fischetti, R. P. Novick, J. J. Ferretti, D. A. Portnoy, and J. I. Rood (ed.), Gram-positive pathogens. ASM Press, Washington, D.C.
49. Novick, R. P., H. F. Ross, S. J. Projan, J. Kornblum, B. Kreiswirth, and S. Moghazeh. 1993. Synthesis of staphylococcal virulence factors is controlled by a regulatory RNA molecule. EMBO J. 12:3967-3975[Medline].
50. Peschel, A., B. Ottenwälder, and F. Götz. 1996. Inducible production and cellular location of the epidermin biosynthetic enzyme EpiQ using an improved staphylococcal expression system. FEMS Microbiol. Lett. 137:279-284[CrossRef][Medline].
51. Pöhlmann-Dietze, P., M. Ulrich, K. B. Kiser, G. Döring, J. C. Lee, J. M. Fournier, K. Botzenhardt, and C. Wolz. 2000. Adherence of Staphylococcus aureus to endothelial cells: influence of capsular polysaccharide, global regulator agr, and bacterial growth phase. Infect. Immun. 68:4865-4871[Abstract/Free Full Text].
52. Ramadurai, L., K. J. Lockwood, M. J. Nadakavukaren, and R. K. Jayaswal. 1999. Characterization of a chromosomally encoded glycylglycine endopeptidase of Staphylococcus aureus. Microbiology 145:801-808[Abstract/Free Full Text].
53. Rechtin, T. M., A. F. Gillaspy, M. A. Schumacher, R. G. Brennan, M. S. Smeltzer, and B. K. Hurlburt. 1999. Characterization of the SarA virulence gene regulator of Staphylococcus aureus. Mol. Microbiol. 33:307-316[CrossRef][Medline].
54. Sambrook, J., E. F. Fritsch, and T. Maniatis. 1989. Molecular cloning: a laboratory manual, 2nd ed. Cold Spring Laboratory Press, Cold Spring Harbor, N.Y.
55. Saravia-Otten, P., H. P. Muller, and S. Arvidson. 1997. Transcription of Staphylococcus aureus fibronectin binding protein genes is negatively regulated by agr and an agr-independent mechanism. J. Bacteriol. 179:5259-5263[Abstract/Free Full Text].
56. Vijay, K., M. S. Brody, E. Fredlund, and C. W. Price. 2000. A PP2C phosphatase containing a PAS domain is required to convey signals of energy stress to the sigmaB transcription factor of Bacillus subtilis. Mol. Microbiol. 35:180-188[CrossRef][Medline].
57. Voelker, U., A. Voelker, B. Maul, M. Hecker, A. Dufour, and W. G. Haldenwang. 1995. Separate mechanisms activate sigma B of Bacillus subtilis in response to environmental and metabolic stresses. J. Bacteriol. 177:3771-3780[Abstract/Free Full Text].
58. Wesson, C. A., L. E. Liou, K. M. Todd, G. A. Bohach, W. R. Trumble, and K. W. Bayles. 1998. Staphylococcus aureus Agr and Sar global regulators influence internalization and induction of apoptosis. Infect. Immun. 66:5238-5243[Abstract/Free Full Text].
59. Wise, A. A., and C. W. Price. 1995. Four additional genes in the sigB operon of Bacillus subtilis that control activity of the general stress factor sigma B in response to environmental signals. J. Bacteriol. 177:123-133[Abstract/Free Full Text].
60. Wolz, C., P. Pöhlmann-Dietze, A. Steinhuber, Y. T. Chien, A. Manna, W. van Wamel, and A. L. Cheung. 2000. Agr-independent regulation of fibronectin-binding protein(s) by the regulatory locus sar in Staphylococcus aureus. Mol. Microbiol. 36:230-243[CrossRef][Medline].
61. Yang, X., C. M. Kang, M. S. Brody, and C. W. Price. 1996. Opposing pairs of serine proteine kinase and phosphatases transmit signals of environmental stress to activate a bacterial transcription factor. Genes Dev. 10:2265-2275[Abstract/Free Full Text].

Journal of Bacteriology, September 2001, p. 5171-5179, Vol. 183, No. 17
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.17.5171-5179.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:

  • Somerville, G. A., Proctor, R. A. (2009). At the Crossroads of Bacterial Metabolism and Virulence Factor Synthesis in Staphylococci. Microbiol. Mol. Biol. Rev. 73: 233-248 [Abstract] [Full Text]  
  • Schulthess, B., Meier, S., Homerova, D., Goerke, C., Wolz, C., Kormanec, J., Berger-Bachi, B., Bischoff, M. (2009). Functional Characterization of the {sigma}B-Dependent yabJ-spoVG Operon in Staphylococcus aureus: Role in Methicillin and Glycopeptide Resistance. Antimicrob. Agents Chemother. 53: 1832-1839 [Abstract] [Full Text]  
  • Truong-Bolduc, Q. C., Ding, Y., Hooper, D. C. (2008). Posttranslational Modification Influences the Effects of MgrA on norA Expression in Staphylococcus aureus. J. Bacteriol. 190: 7375-7381 [Abstract] [Full Text]  
  • Seidl, K., Bischoff, M., Berger-Bachi, B. (2008). CcpA Mediates the Catabolite Repression of tst in Staphylococcus aureus. Infect. Immun. 76: 5093-5099 [Abstract] [Full Text]  
  • Tsuji, B. T., von Eiff, C., Kelchlin, P. A., Forrest, A., Smith, P. F. (2008). Attenuated Vancomycin Bactericidal Activity against Staphylococcus aureus hemB Mutants Expressing the Small-Colony-Variant Phenotype. Antimicrob. Agents Chemother. 52: 1533-1537 [Abstract] [Full Text]  
  • Cheung, A. L., Nishina, K., Manna, A. C. (2008). SarA of Staphylococcus aureus Binds to the sarA Promoter To Regulate Gene Expression. J. Bacteriol. 190: 2239-2243 [Abstract] [Full Text]  
  • Adhikari, R. P., Novick, R. P. (2008). Regulatory organization of the staphylococcal sae locus. Microbiology 154: 949-959 [Abstract] [Full Text]  
  • Meier, S., Goerke, C., Wolz, C., Seidl, K., Homerova, D., Schulthess, B., Kormanec, J., Berger-Bachi, B., Bischoff, M. (2007). {sigma}B and the {sigma}B-Dependent arlRS and yabJ-spoVG Loci Affect Capsule Formation in Staphylococcus aureus. Infect. Immun. 75: 4562-4571 [Abstract] [Full Text]  
  • Cassat, J., Dunman, P. M., Murphy, E., Projan, S. J., Beenken, K. E., Palm, K. J., Yang, S.-J., Rice, K. C., Bayles, K. W., Smeltzer, M. S. (2006). Transcriptional profiling of a Staphylococcus aureus clinical isolate and its isogenic agr and sarA mutants reveals global differences in comparison to the laboratory strain RN6390.. Microbiology 152: 3075-3090 [Abstract] [Full Text]  
  • Shaw, L. N., Aish, J., Davenport, J. E., Brown, M. C., Lithgow, J. K., Simmonite, K., Crossley, H., Travis, J., Potempa, J., Foster, S. J. (2006). Investigations into {sigma}B-Modulated Regulatory Pathways Governing Extracellular Virulence Determinant Production in Staphylococcus aureus.. J. Bacteriol. 188: 6070-6080 [Abstract] [Full Text]  
  • Sambanthamoorthy, K., Smeltzer, M. S., Elasri, M. O. (2006). Identification and characterization of msa (SA1233), a gene involved in expression of SarA and several virulence factors in Staphylococcus aureus.. Microbiology 152: 2559-2572 [Abstract] [Full Text]  
  • Palma, M., Bayer, A., Kupferwasser, L. I., Joska, T., Yeaman, M. R., Cheung, A. (2006). Salicylic Acid Activates Sigma Factor B by rsbU-Dependent and -Independent Mechanisms.. J. Bacteriol. 188: 5896-5903 [Abstract] [Full Text]  
  • Morikawa, K., Ohniwa, R. L., Kim, J., Maruyama, A., Ohta, T., Takeyasu, K. (2006). Bacterial nucleoid dynamics: oxidative stress response in Staphylococcus aureus. GENES CELLS 11: 409-423 [Abstract] [Full Text]  
  • Moisan, H., Brouillette, E., Jacob, C. L., Langlois-Begin, P., Michaud, S., Malouin, F. (2006). Transcription of Virulence Factors in Staphylococcus aureus Small-Colony Variants Isolated from Cystic Fibrosis Patients Is Influenced by SigB. J. Bacteriol. 188: 64-76 [Abstract] [Full Text]  
  • Kazmierczak, M. J., Wiedmann, M., Boor, K. J. (2005). Alternative Sigma Factors and Their Roles in Bacterial Virulence. Microbiol. Mol. Biol. Rev. 69: 527-543 [Abstract] [Full Text]  
  • Senn, M. M., Giachino, P., Homerova, D., Steinhuber, A., Strassner, J., Kormanec, J., Fluckiger, U., Berger-Bachi, B., Bischoff, M. (2005). Molecular Analysis and Organization of the {sigma}B Operon in Staphylococcus aureus. J. Bacteriol. 187: 8006-8019 [Abstract] [Full Text]  
  • Senn, M. M., Bischoff, M., von Eiff, C., Berger-Bachi, B. (2005). {sigma}B Activity in a Staphylococcus aureus hemB Mutant. J. Bacteriol. 187: 7397-7406 [Abstract] [Full Text]  
  • Liang, X., Zheng, L., Landwehr, C., Lunsford, D., Holmes, D., Ji, Y. (2005). Global Regulation of Gene Expression by ArlRS, a Two-Component Signal Transduction Regulatory System of Staphylococcus aureus. J. Bacteriol. 187: 5486-5492 [Abstract] [Full Text]  
  • Sakoulas, G., Eliopoulos, G. M., Fowler, V. G. Jr., Moellering, R. C. Jr., Novick, R. P., Lucindo, N., Yeaman, M. R., Bayer, A. S. (2005). Reduced Susceptibility of Staphylococcus aureus to Vancomycin and Platelet Microbicidal Protein Correlates with Defective Autolysis and Loss of Accessory Gene Regulator (agr) Function. Antimicrob. Agents Chemother. 49: 2687-2692 [Abstract] [Full Text]  
  • Kahl, B. C., Belling, G., Becker, P., Chatterjee, I., Wardecki, K., Hilgert, K., Cheung, A. L., Peters, G., Herrmann, M. (2005). Thymidine-Dependent Staphylococcus aureus Small-Colony Variants Are Associated with Extensive Alterations in Regulator and Virulence Gene Expression Profiles. Infect. Immun. 73: 4119-4126 [Abstract] [Full Text]  
  • Goerke, C., Fluckiger, U., Steinhuber, A., Bisanzio, V., Ulrich, M., Bischoff, M., Patti, J. M., Wolz, C. (2005). Role of Staphylococcus aureus Global Regulators sae and {sigma}B in Virulence Gene Expression during Device-Related Infection. Infect. Immun. 73: 3415-3421 [Abstract] [Full Text]  
  • Harraghy, N., Kormanec, J., Wolz, C., Homerova, D., Goerke, C., Ohlsen, K., Qazi, S., Hill, P., Herrmann, M. (2005). sae is essential for expression of the staphylococcal adhesins Eap and Emp. Microbiology 151: 1789-1800 [Abstract] [Full Text]  
  • Zhang, H., Morikawa, K., Ohta, T., Kato, Y. (2005). In vitro resistance to the CS{alpha}{beta}-type antimicrobial peptide ASABF- is conferred by overexpression of sigma factor sigB in Staphylococcus aureus. J Antimicrob Chemother 55: 686-691 [Abstract] [Full Text]  
  • Li, D., Renzoni, A., Estoppey, T., Bisognano, C., Francois, P., Kelley, W. L., Lew, D. P., Schrenzel, J., Vaudaux, P. (2005). Induction of Fibronectin Adhesins in Quinolone-Resistant Staphylococcus aureus by Subinhibitory Levels of Ciprofloxacin or by Sigma B Transcription Factor Activity Is Mediated by Two Separate Pathways. Antimicrob. Agents Chemother. 49: 916-924 [Abstract] [Full Text]  
  • Entenza, J.-M., Moreillon, P., Senn, M. M., Kormanec, J., Dunman, P. M., Berger-Bachi, B., Projan, S., Bischoff, M. (2005). Role of {sigma}B in the Expression of Staphylococcus aureus Cell Wall Adhesins ClfA and FnbA and Contribution to Infectivity in a Rat Model of Experimental Endocarditis. Infect. Immun. 73: 990-998 [Abstract] [Full Text]  
  • Renzoni, A., Francois, P., Li, D., Kelley, W. L., Lew, D. P., Vaudaux, P., Schrenzel, J. (2004). Modulation of Fibronectin Adhesins and Other Virulence Factors in a Teicoplanin-Resistant Derivative of Methicillin-Resistant Staphylococcus aureus. Antimicrob. Agents Chemother. 48: 2958-2965 [Abstract] [Full Text]  
  • Wang, L., Trawick, J. D., Yamamoto, R., Zamudio, C. (2004). Genome-wide operon prediction in Staphylococcus aureus. Nucleic Acids Res 32: 3689-3702 [Abstract] [Full Text]  
  • Knobloch, J. K.-M., Jager, S., Horstkotte, M. A., Rohde, H., Mack, D. (2004). RsbU-Dependent Regulation of Staphylococcus epidermidis Biofilm Formation Is Mediated via the Alternative Sigma Factor {sigma}B by Repression of the Negative Regulator Gene icaR. Infect. Immun. 72: 3838-3848 [Abstract] [Full Text]  
  • Bischoff, M., Dunman, P., Kormanec, J., Macapagal, D., Murphy, E., Mounts, W., Berger-Bachi, B., Projan, S. (2004). Microarray-Based Analysis of the Staphylococcus aureus {sigma}B Regulon. J. Bacteriol. 186: 4085-4099 [Abstract] [Full Text]  
  • Rice, K. C., Patton, T., Yang, S.-J., Dumoulin, A., Bischoff, M., Bayles, K. W. (2004). Transcription of the Staphylococcus aureus cid and lrg Murein Hydrolase Regulators Is Affected by Sigma Factor B. J. Bacteriol. 186: 3029-3037 [Abstract] [Full Text]  
  • Tseng, C. W., Zhang, S., Stewart, G. C. (2004). Accessory Gene Regulator Control of Staphyloccoccal Enterotoxin D Gene Expression. J. Bacteriol. 186: 1793-1801 [Abstract] [Full Text]  
  • Bisognano, C., Kelley, W. L., Estoppey, T., Francois, P., Schrenzel, J., Li, D., Lew, D. P., Hooper, D. C., Cheung, A. L., Vaudaux, P. (2004). A RecA-LexA-dependent Pathway Mediates Ciprofloxacin-induced Fibronectin Binding in Staphylococcus aureus. J. Biol. Chem. 279: 9064-9071 [Abstract] [Full Text]  
  • Shaw, L., Golonka, E., Potempa, J., Foster, S. J. (2004). The role and regulation of the extracellular proteases of Staphylococcus aureus. Microbiology 150: 217-228 [Abstract] [Full Text]  
  • Steinhuber, A., Goerke, C., Bayer, M. G., Doring, G., Wolz, C. (2003). Molecular Architecture of the Regulatory Locus sae of Staphylococcus aureus and Its Impact on Expression of Virulence Factors. J. Bacteriol. 185: 6278-6286 [Abstract] [Full Text]  
  • Kazmierczak, M. J., Mithoe, S. C., Boor, K. J., Wiedmann, M. (2003). Listeria monocytogenes {sigma}B Regulates Stress Response and Virulence Functions. J. Bacteriol. 185: 5722-5734 [Abstract] [Full Text]  
  • Schmidt, K. A., Manna, A. C., Cheung, A. L. (2003). SarT Influences sarS Expression in Staphylococcus aureus. Infect. Immun. 71: 5139-5148 [Abstract] [Full Text]  
  • Rossi, J., Bischoff, M., Wada, A., Berger-Bachi, B. (2003). MsrR, a Putative Cell Envelope-Associated Element Involved in Staphylococcus aureus sarA Attenuation. Antimicrob. Agents Chemother. 47: 2558-2564 [Abstract] [Full Text]  
  • Nair, S. P., Bischoff, M., Senn, M. M., Berger-Bachi, B. (2003). The {sigma}B Regulon Influences Internalization of Staphylococcus aureus by Osteoblasts. Infect. Immun. 71: 4167-4170 [Abstract] [Full Text]  
  • Beenken, K. E., Blevins, J. S., Smeltzer, M. S. (2003). Mutation of sarA in Staphylococcus aureus Limits Biofilm Formation. Infect. Immun. 71: 4206-4211 [Abstract] [Full Text]  
  • Luong, T. T., Newell, S. W., Lee, C. Y. (2003). mgr, a Novel Global Regulator in Staphylococcus aureus. J. Bacteriol. 185: 3703-3710 [Abstract] [Full Text]  
  • Ferreira, A., Sue, D., O'Byrne, C. P., Boor, K. J. (2003). Role of Listeria monocytogenes{sigma}B in Survival of Lethal Acidic Conditions and in the Acquired Acid Tolerance Response. Appl. Environ. Microbiol. 69: 2692-2698 [Abstract] [Full Text]  
  • Sifri, C. D., Begun, J., Ausubel, F. M., Calderwood, S. B. (2003). Caenorhabditis elegans as a Model Host for Staphylococcus aureus Pathogenesis. Infect. Immun. 71: 2208-2217 [Abstract] [Full Text]  
  • Said-Salim, B., Dunman, P. M., McAleese, F. M., Macapagal, D., Murphy, E., McNamara, P. J., Arvidson, S., Foster, T. J., Projan, S. J., Kreiswirth, B. N. (2003). Global Regulation of Staphylococcus aureus Genes by Rot. J. Bacteriol. 185: 610-619 [Abstract] [Full Text]  
  • Blevins, J. S., Elasri, M. O., Allmendinger, S. D., Beenken, K. E., Skinner, R. A., Thomas, J. R., Smeltzer, M. S. (2003). Role of sarA in the Pathogenesis of Staphylococcus aureus Musculoskeletal Infection. Infect. Immun. 71: 516-523 [Abstract] [Full Text]  
  • Price, C. T. D., Singh, V. K., Jayaswal, R. K., Wilkinson, B. J., Gustafson, J. E. (2002). Pine Oil Cleaner-Resistant Staphylococcus aureus: Reduced Susceptibility to Vancomycin and Oxacillin and Involvement of SigB. Appl. Environ. Microbiol. 68: 5417-5421 [Abstract] [Full Text]  
  • Horsburgh, M. J., Aish, J. L., White, I. J., Shaw, L., Lithgow, J. K., Foster, S. J. (2002). {sigma}B Modulates Virulence Determinant Expression and Stress Resistance: Characterization of a Functional rsbU Strain Derived from Staphylococcus aureus 8325-4. J. Bacteriol. 184: 5457-5467 [Abstract] [Full Text]  
  • Cordwell, S. J., Larsen, M. R., Cole, R. T., Walsh, B. J. (2002). Comparative proteomics of Staphylococcus aureus and the response of methicillin-resistant and methicillin-sensitive strains to Triton X-100. Microbiology 148: 2765-2781 [Abstract] [Full Text]  
  • Karlsson, A., Arvidson, S. (2002). Variation in Extracellular Protease Production among Clinical Isolates of Staphylococcus aureus Due to Different Levels of Expression of the Protease Repressor sarA. Infect. Immun. 70: 4239-4246 [Abstract] [Full Text]  
  • Wolz, C., Goerke, C., Landmann, R., Zimmerli, W., Fluckiger, U. (2002). Transcription of Clumping Factor A in Attached and Unattached Staphylococcus aureus In Vitro and during Device-Related Infection. Infect. Immun. 70: 2758-2762 [Abstract] [Full Text]  
  • Sakoulas, G., Eliopoulos, G. M., Moellering, R. C. Jr., Wennersten, C., Venkataraman, L., Novick, R. P., Gold, H. S. (2002). Accessory Gene Regulator (agr) Locus in Geographically Diverse Staphylococcus aureus Isolates with Reduced Susceptibility to Vancomycin. Antimicrob. Agents Chemother. 46: 1492-1502 [Abstract] [Full Text]  
  • Blevins, J. S., Beenken, K. E., Elasri, M. O., Hurlburt, B. K., Smeltzer, M. S. (2002). Strain-Dependent Differences in the Regulatory Roles of sarA and agr in Staphylococcus aureus. Infect. Immun. 70: 470-480 [Abstract] [Full Text]  

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bischoff, M.
Right arrow Articles by Giachino, P.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bischoff, M.
Right arrow Articles by Giachino, P.

Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»