SarZ inhibits the hemolytic activity through regulation of phenol soluble modulins in .

BACKGROUND

is an important conditionally pathogenic bacterium. SarZ, belonging to the SarA family protein, has been demonstrated in to promote the expression of invasive virulence factors while inhibiting biofilm formation. However, the regulatory role of SarZ on virulence is not completely understood.

RESULTS

In this study, we successfully deleted the gene by allelic replacement in . The mutant strain exhibited remarkably increased hemolytic activity and drastically impaired biofilm formation, suggesting that SarZ is key regulator of virulence in . Through butanol extraction of the spent medium and HPLC-MS/MS analysis, production of phenol soluble modulins (PSMs) possessing cytolytic effect was found to be elevated significantly in the mutant. Subsequent qRT-PCR experiments demonstrated that expression of the genes, especially the β-type, was upregulated dramatically in the mutant. Meanwhile, transcription of gene responsible for biofilm formation was sharply diminished. The double mutant was further generated and displayed a significantly decreased hemolytic activity compared with the mutant. EMSA assays implied that recombinant SarZ protein can directly bind to the promoter regions of the and operon. DNase I footprinting assays further pinpointed two SarZ-binding sites on the operon promoter.

CONCLUSION

Taken together, the results confirmed that SarZ is a pivotal regulator of virulence in and might respectively regulate the hemolytic activity and biofilm formation mainly by directly controlling the transcription of genes, particularly the β-type, and the operon.