A role for sigma factor B in the emergence of Staphylococcus aureus small-colony variants and elevated biofilm production resulting from an exposure to aminoglycosides

2010 ◽  
Vol 48 (1) ◽  
pp. 18-27 ◽  
Author(s):  
Gabriel Mitchell ◽  
Eric Brouillette ◽  
David Lalonde Séguin ◽  
Ann-Elise Asselin ◽  
Christian Lebeau Jacob ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Sigma Factor ◽  
Factor B ◽  
Small Colony Variants ◽  
Biofilm Production ◽  
Sigma Factor B ◽  
Small Colony

scholarly journals Transcription of the Staphylococcus aureus cid and lrg Murein Hydrolase Regulators Is Affected by Sigma Factor B

2004 ◽  
Vol 186 (10) ◽  
pp. 3029-3037 ◽  
Author(s):  
Kelly C. Rice ◽  
Toni Patton ◽  
Soo-Jin Yang ◽  
Alexis Dumoulin ◽  
Markus Bischoff ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Northern Blot ◽  
Exponential Growth ◽  
Sigma Factor ◽  
Positive Impact ◽  
Consensus Sequence ◽  
Hydrolase Activity ◽  
Factor B ◽  
Sigma Factor B ◽  
Murein Hydrolase

ABSTRACT The Staphylococcus aureus lrg and cid loci are homologous operons that have been shown to regulate murein hydrolase activity and affect sensitivity to penicillin. Although the mode of action of these operons has not been demonstrated, a model based on the similarities of the lrgA and cidA gene products to the bacteriophage holin family of proteins has been proposed. In this study, the transcription organization and regulation of these operons were examined by Northern blot analyses. Unexpectedly, cidB and a gene located immediately downstream, designated cidC, were found to be cotranscribed on a 2.7-kb transcript. Maximal cidBC transcription occurred during early exponential growth, and high-level transcription of cidBC was dependent on the rsbU-mediated activation of the alternative sigma factor B (σB). In contrast, lrgAB transcription in stationary phase was negatively regulated by σB. Although cidABC transcription was not detected by Northern blot analysis, reverse transcriptase PCR revealed that these genes are also cotranscribed as a single RNA message in early exponential growth. Primer extension analysis revealed the presence of two cidBC transcription start sites, but no apparent σB-dependent promoter consensus sequence was identified in these regions. The rsbU gene was also shown to have a positive impact on murein hydrolase activity but a negligible effect on sensitivity to penicillin-induced killing. These results suggest that the lrgAB and cidBC genes may be part of the S. aureus σB-controlled stress regulon.

scholarly journals Sigma Factor B and RsbU Are Required for Virulence in Staphylococcus aureus-Induced Arthritis and Sepsis

2004 ◽  
Vol 72 (10) ◽  
pp. 6106-6111 ◽  
Author(s):  
Ing-Marie Jonsson ◽  
Staffan Arvidson ◽  
Simon Foster ◽  
Andrzej Tarkowski
Keyword(s):  
Staphylococcus Aureus ◽  
Sigma Factor ◽  
Staphylococcal Infection ◽  
Factor B ◽  
Isogenic Strain ◽  
Severe Arthritis ◽  
Sigma Factor B ◽  
Weight Decrease ◽  
Intravenous Inoculation ◽  
Negative Mutant

ABSTRACT The prototype Staphylococcus aureus strain 8325-4 produces high levels of hemolysins and proteases. Recently it has been shown that this property depends on a deficiency of sigma factor B (SigB) activity controlling the activation of regulatory genes such as agr and sarA. SigB deficiency is in turn due to a mutation in the rsbU gene, which is required for posttranslational activation of SigB. The rsbU defect of strain 8325-4 has recently been repaired, and we used this strain (SH1000), along with its isogenic sigB-negative mutant, to investigate the contributions of RsbU and SigB in a murine model of septic arthritis. Intravenous inoculation with the rsbU-repaired isogenic strain SH1000 resulted in significantly more severe arthritis, weight decrease, and mortality compared to those of the parental strain 8325-4 (rsbU-negative) or the isogenic sigB-negative mutant (MJH502). SH1000 also persisted more in kidneys and joints of infected mice. Our data strongly suggest that RsbU and SigB regulate important virulence factors, thereby contributing significantly to the outcome of staphylococcal infection.

scholarly journals Variation in Extracellular Protease Production among Clinical Isolates of Staphylococcus aureus Due to Different Levels of Expression of the Protease Repressor sarA

2002 ◽  
Vol 70 (8) ◽  
pp. 4239-4246 ◽  
Author(s):  
Anna Karlsson ◽  
Staffan Arvidson
Keyword(s):  
Staphylococcus Aureus ◽  
Sigma Factor ◽  
Northern Blotting ◽  
Protease Production ◽  
Extracellular Proteases ◽  
Factor B ◽  
Human Soft Tissue ◽  
Sigma Factor B ◽  
Different Levels

ABSTRACT Staphylococcus aureus produces four major extracellular proteases: staphylococcal serine protease (V8 protease; SspA), cysteine protease (SspB), metalloprotease (aureolysin; Aur), and staphopain (Scp). Several in vitro studies have suggested that these enzymes are important virulence factors. Here we analyzed the protease production of 92 S. aureus strains from infected human soft tissue. Twenty-one strains produced variable zones of proteolysis on casein agar plates, while the remaining 71 strains appeared to be protease negative. The major protease genes were present in all protease-positive (n = 5) and protease-negative (n = 12) strains analyzed. Northern blotting showed that transcription of the protease genes was suppressed due to increased sigma factor B (SigB)-dependent expression of the protease repressor SarA. Other SigB-dependent traits such as pigmentation and expression of asp 23 were also increased in protease-negative compared to protease-positive strains. Inactivation of sarA in three protease-negative strains resulted in increased transcription of all protease genes and increased protease production, while overexpression of sarA in a strain producing protease at high levels repressed protease production. Our results suggest that the protease genes are conserved among clinical S. aureus strains and that the level of SigB-dependent expression of the protease repressor sarA determines the level of protease production in each strain.

scholarly journals Isolation and Characterization of a sigBDeletion Mutant of Staphylococcus aureus

1999 ◽  
Vol 67 (7) ◽  
pp. 3667-3669 ◽  
Author(s):  
R. O. Nicholas ◽  
Tong Li ◽  
D. McDevitt ◽  
Andrea Marra ◽  
S. Sucoloski ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Sigma Factor ◽  
No Reduction ◽  
Infection Model ◽  
Factor B ◽  
Allelic Replacement ◽  
Isolation And Characterization ◽  
Sigma Factor B

ABSTRACT The sigB gene of Staphylococcus aureus, coding for the alternate sigma factor B, has been deleted by allelic replacement mutagenesis. The mutant grew as well as the parent in vitro, although it was deficient in clumping factor, coagulase, and pigment. In two murine and one rat infection model the mutant showed no reduction in virulence.

Properties and control of cold-induced small colony variants of Staphylococcus aureus

2020 ◽  
pp. 100874
Author(s):  
Jiaju Qiao ◽  
Mengjiao Zhu ◽  
Yun Fan ◽  
Zhaoxin Lu ◽  
Fengxia Lv ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Small Colony Variants ◽  
Small Colony ◽  
And Control
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