Regulation of exoprotein expression in Staphylococcus aureus by a locus (sar) distinct from agr.

Abstract

A single insertion of transposon Tn917LTV1 into the chromosome ofa Staphylococcus aureus Cdinical isolate, strain DB, resulted in a pleiotropic effect on the expression of a number of extraceilular and cell-wall-as ted proteins. Detailed comparison ofphenotype associated with the mutant, 11D2, and the parent, DB, indicted that the chromosomal locus inactivated as a result of transposon mutagenesis differs from the S. aureus accessory gene regulator locus (agr). In particular, the expression of a-hemolysin, which is not detectable in Agr mutants, was enhanced in mutant 11D2, while it remained at a low level in strain DB. Likewise, protease activity was significantly enhanced in 11D2 compared with DB. In addition, most of the cell-bound proteins were expressed at lower levels in the mutant than the parent strain. This pattern is contrary to that found in switching from Agr+ to Agrphenotypes. Southern blot hybridization with an agr probe indicated that the inactivated chromosomal locus is distinct from agr. Transduction experiments demonstrated that the phenotypes associated with mutant 11D2 could be transferred to the parental strain DB as well as to RN450, an S. aureus strain with a genetic background similar to strain 8325-4. This locus on the S. aureus chromosome, possibly regulatory in nature, has been designated sar for staphylococcal accessory regulator.

Alternative transcription factor sigmaSB of Staphylococcus aureus: characterization and role in transcription of the global regulatory locus sar

“…S. aureus causes a number of infections ranging from superficial skin abscesses to life-threatening systemic diseases (e.g., toxic shock syndrome and osteomyelitis) (17,25,38). The synthesis of a variety of extracellular and cell surface proteins involved in the pathogenesis of S. aureus has been shown to be controlled by at least two global regulatory elements, agr and sar (4,5,12,13,23,26,27,29,32,34). The agr system is the best characterized of these elements and responds to environmental stimuli, thereby resulting in the elevated synthesis of extracellular toxins with a concomitant decrease of the synthesis of surface proteins.…”

Cloning and sequencing of sarA of Staphylococcus aureus, a gene required for the expression of agr

“…Inactivation of this locus by Tn917LTV1 insertion has resulted in decreased expression of several extracellular (e.g., ,B-hemolysin) and cell wall proteins (3). Phenotypic, Southern blot, and genetic mapping analyses indicated that this locus is distinct from agr and xpr (3,4). Using the DNA sequence flanking the Tn917LTV1 insertion as a probe, we have subsequently cloned and sequenced the sar gene that is involved in the regulation of exoprotein synthesis., Additional transcriptional and phenotypic studies revealed that this sar gene is necessary for the optimal expression of agr.…”

“…We recently reported an additional locus in S. aureus, designated sar, that is involved in the regulation of exoproteins (3). Inactivation of this locus by Tn917LTV1 insertion has resulted in decreased expression of several extracellular (e.g., ,B-hemolysin) and cell wall proteins (3).…”

“…In S. aureus, the postexponential-phase regulation of virulence determinants and other exoprotein genes involves at least three global regulatory systems, agr, xpr, and sar (3,11,20). Most of the exoprotein regulated by agr are either not synthesized or synthesized at a reduced rate in agr mutants, while the synthesis of surface proteins is upregulated (11).…”

“…The bacterial strains and plasmids used in this study are listed in Table 1. Phage d?11 was used as a transducing phage for strains RN4220, RN450, and RN6390 (3). The following media were used for bacterial growth: CYGP broth for S. aureus (15) and Luria-Bertani broth for Escherichia coli (13).…”