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Updated: Aug 23, 2026

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
Control of virulence by the two-component system CiaR/H is mediated via HtrA, a major virulence factor of
Yasser Musa Ibrahim1, Alison R Kerr, Jackie McCluskey
1Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, G12-8QQ, United Kingdom.
Abstract:
The CiaR/H two-component system is involved in regulating virulence and competence in Streptococcus pneumoniae. The system is known to regulate many genes, including that for high-temperature requirement A (HtrA). This gene has been implicated in the ability of the pneumococcus to colonize the nasopharynx of infant rats. We reported previously that deletion of the gene for HtrA made the pneumococcal strains much less virulent in mouse models, less able to grow at higher temperatures, and more sensitive to oxidative stress. In this report, we show that the growth phenotype as well as sensitivity to oxidative stress of Delta ciaR mutant was very similar to that of a Delta htrA mutant and that the expression of the HtrA protein was reduced in a ciaR-null mutant. Both the in vitro phenotype and the reduced virulence of Delta ciaR mutant could be restored by increasing the expression of HtrA.
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