| Abstrakt: |
ABSTRACTStreptococcus pyogenesis a ubiquitous and versatile pathogen that causes a variety of infections with a wide range of severity. The versatility of this organism is due in part to its capacity to regulate virulence gene expression in response to the many environments that it encounters during an infection. We analyzed the expression of two potential virulence factors, sagAand siaA(also referred to as peland htsA, respectively), in response to conditions of varying cell densities and iron concentrations. The sagAgene was up-regulated in conditioned medium from a wild-type strain but not from sagA-deficient mutants, and the gene was also up-regulated in the presence of streptolysin S (SLS), the gene product of sagA, thus indicating that this gene or its product is involved in density-dependent regulation of S. pyogenes. By comparison, siaAresponded in a manner consistent with a role in iron acquisition since it was up-regulated under iron-restricted conditions. Although siaAexpression was also up-regulated in the presence of SLS and in conditioned media from both wild-type and sagA-deficient mutants, this up-regulation was not growth phase dependent. We conclude that sagAencodes a quorum-sensing signaling molecule, likely SLS, and further support the notion that siaAis likely involved in iron acquisition. |
