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Updated: Jun 13, 2026

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
Inactivation of DNA-binding response regulator Sak189 abrogates beta-antigen expression and affects virulence of
Anastasia S Rozhdestvenskaya1, Artem A Totolian, Alexander V Dmitriev
1Department of Molecular Microbiology, Institute of Experimental Medicine, Saint-Petersburg, Russia.
Background:
Streptococcus agalactiae is able to colonize numerous tissues employing different mechanisms of gene regulation, particularly via two-component regulatory systems. These systems sense the environmental stimuli and regulate expression of the genes including virulence genes. Recently, the novel two-component regulatory system Sak188/Sak189 was identified. In S. agalactiae genome, it was adjacent to the bac gene encoding for beta-antigen, an important virulence factor.
Methodology/Principal Findings:
In this study, the sak188 and sak189 genes were inactivated, and the functional role of Sak188/Sak189 two-component system in regulation of the beta-antigen expression was investigated. It was demonstrated that both transcription of bac gene and expression of encoded beta-antigen were controlled by Sak189 response regulator, but not Sak188 histidine kinase. It was also found that the regulation occurred at transcriptional level. Finally, insertional inactivation of sak189 gene, but not sak188 gene, significantly affected virulent properties of S. agalactiae.
Conclusions/Significance:
Sak189 response regulator is necessary for activation of bac gene transcription. It also controls the virulent properties of S. agalactiae. Given that the primary functional role of Sak188/Sak189 two-component systems is a control of bac gene transcription, this system can be annotated as BgrR/S (bacgene regulatory system).
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