Natural human isolates of Staphylococcus aureus selected for high production of proteases and alpha-hemolysin are sigmaB deficient

Int J Med Microbiol. 2006 Aug;296(4-5):229-36. doi: 10.1016/j.ijmm.2006.01.067. Epub 2006 Mar 10.


It has been reported that high production of proteases and alpha-hemolysin in the prototype Staphylococcus aureus strain 8325-4 was associated with its sigmaB deficiency. Here we analyzed one fresh clinical isolate (KS26) and two ancient human isolates (Wood46 and V8) selected for high production of proteases and alpha-hemolysin. All three strains lacked yellow pigment and showed a low level of expression of sigB-dependent promoters, indicating sigmaB deficiency. Nucleotide sequencing of the sigB operon revealed that KS26 and Wood46 had stop codons in rsbU and sigB, respectively, while V8 had an insertion of an IS element in rsbU. Complementation experiments with sigB on a plasmid reduced expression of proteases and alpha-hemolysin dramatically, indicating that the high production of these exoproteins was associated with sigmaB deficiency. Although sigmaB-deficient strains show attenuated virulence in some animal models, our results indicate that such strains can cause infection in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / physiology
  • Bacterial Toxins / biosynthesis*
  • Blotting, Northern
  • Blotting, Southern
  • Codon, Nonsense
  • Codon, Terminator
  • DNA Transposable Elements
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Gene Expression Regulation, Bacterial*
  • Genetic Complementation Test
  • Hemolysin Proteins
  • Molecular Sequence Data
  • Peptide Hydrolases / biosynthesis*
  • Promoter Regions, Genetic
  • RNA, Bacterial / analysis
  • RNA, Messenger / analysis
  • Recombination, Genetic
  • Regulon / physiology
  • Sequence Analysis, DNA
  • Sigma Factor / genetics*
  • Sigma Factor / physiology
  • Staphylococcus aureus / enzymology*
  • Staphylococcus aureus / genetics*


  • Bacterial Proteins
  • Bacterial Toxins
  • Codon, Nonsense
  • Codon, Terminator
  • DNA Transposable Elements
  • DNA, Bacterial
  • Hemolysin Proteins
  • RNA, Bacterial
  • RNA, Messenger
  • SigB protein, Bacteria
  • Sigma Factor
  • staphylococcal alpha-toxin
  • Peptide Hydrolases

Associated data

  • GENBANK/AJ891047
  • GENBANK/AJ891048
  • GENBANK/AJ920004