Characterization of SivS/R, a Two-component Signal Transduction System in Streptococcus Iniae

Released on by Shelly Bolotin
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  • Characterization of SivS/R, a Two-component Signal Transduction System in Streptococcus Iniae Book Detail

  • Author : Shelly Bolotin
  • Release Date : 2007
  • Publisher :
  • Genre :
  • Pages : 280
  • ISBN 13 : 9780494395325
  • File Size : 39,39 MB
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Characterization of SivS/R, a Two-component Signal Transduction System in Streptococcus Iniae by Shelly Bolotin PDF Summary

Book Description: Streptococcus iniae causes invasive disease and death in fish, as well as soft-tissue infections in humans. A two-component signal transduction system (TCS), sivS/R, was identified using Tn917 transposon screening. This TCS was characterized using a deletion-insertion mutant, termed 9117Deltasiv, which was constructed using a PCR ligation technique. Transmission electron microscopy (TEM) showed that 9117Deltasiv exhibited aberrant asymmetric septae that resulted in clumps of irregularly shaped cells. Exopolysaccharide (EPS) was present on the surface of the parent strain but not 9117Deltasiv. Whole human blood killing assays demonstrated that the mutant, unlike the parent strain, was susceptible to phagocytosis. Mutant 9117Delta siv also exhibited reduced virulence when injected subcutaneously in a mouse and caused only transient bacteremia compared to the parent strain. Real-time PCR showed that in the mutant, transcription of cpsA, the first gene in the S. iniae capsule operon, was reduced, indicating a role of sivS/R in the regulation of this gene. In addition, real-time PCR studies indicated that SivS/R regulates expression levels of the streptolysin S structural gene, sagA, as well as the CAMP factor gene, cfi. Furthermore, SDS-PAGE of the S. iniae spheroplast revealed downregulation of three surface proteins in the mutant strain compared to the parent strain. These proteins were identified by mass spectrometry to be a putative lipoprotein, a hyaluronate associated protein and a pyruvate kinase. In addition to exhibiting attenuated virulence, 9117Deltasiv, unlike its parent strain, was unable to grow using malate as a carbon source. Real time PCR demonstrated that unlike the parent strain, which was upregulated twenty fold when induced by malate, 9117Delta siv did not upregulate expression of the malate permease gene malP in response to malate, indicating that SivS/R controls malate metabolism through transcriptional control of malP. In conclusion, this work demonstrates that SivS/R regulates a number of genes in S. iniae, including those involved in both virulence and malate metabolism.

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