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Updated: Aug 8, 2026

A Fluorescence-based Method to Study Bacterial Gene Regulation in Infected Tissues
Published on: February 19, 2019
Expression of gamma-hemolysin regulated by sae in Staphylococcus aureus strain Smith 5R
Kazuko Yamazaki1, Fuminori Kato, Yoshiyuki Kamio
1Laboratory of Applied Microbiology, Department of Microbial Biotechnology, Graduate School of Agricultural Science, Tohoku University, Sendai, Japan.
Abstract:
Staphylococcus aureus strain Smith 5R produces a two-component pore-forming toxin and forms a rough-surfaced colony with hemolytic haloes on human red blood cell plates (R[+]). Serial subcultures of the strain in broth caused the appearance of gamma-hemolysin negative variants with a smooth colony shape (S[-]), and the S[-] valiant became predominant in culture. The R[+] strain, in which agrA is naturally disrupted by an insertion of IS1181, produced high levels of gamma-hemolysin. In the S[-] variant, expression of both hlg and lukS-F mRNAs was strongly reduced. Nucleotide sequencing of the sae locus revealed that all isolated S[-] variants had spontaneous mutations in the sae locus. Recovery of gamma-hemolysin productivity in S[-] by transformation of the wild-type sae allele strongly suggested that the expression of gamma-hemolysin is positively regulated by sae in an agr-independent manner.
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