Effect of knockout and overexpression of the Streptococcus pneumoniae topoisomerase I regulator StaR on gene expression.

Strain ?staRPZnstaR was obtained to investigate genome-wide differential gene expresion when staR gene is reppressed or overexpressed by adding Zn to the culture medium. In addition, gene expression profile alterations produced upon inhibition of gyrase with Novobiocin were studied in the absence and presence of StaR. Overall design: Cultures were grown to OD620nm = 0.2, diluted 50-fold in medium either without ZnSO4 (staR repressed) or with 150 µM ZnSO4 (staR activated) and grown to OD620nm = 0.4. Samples were taken at this point for the comparative gene expression profiling analysis of RNA-seq when staR was repressed or over-expressed (two biological replicates). Then, novobiocin was added to the cultures and they were grown for 30 additional min, while the same ZnSO4 concentration was maintained. Samples were taken at this point for the comparative gene expression profiling analysis of RNA-seq when gyrase is inhibited with novobiocin in the absence or in the presence of StaR. Two biological replicates were analyzed.