Roles of relSpn in Stringent Response, Global Regulation, and Virulence of Serotype 2 Streptococcus pneumoniae D39. Streptococcus pneumoniae

Transcriptome analysis of D39 rel+Spn and delta-relSpn strains treated with mupirocin revealed relSpn-independent (translation stress), relSpn-dependent (stringent response), and delta-relSpn-dependent changes suggesting that relSpn and (p)ppGpp amount play wide-ranging homeostatic roles in pneumococcal physiology, besides adjusting macromolecular synthesis and transport in response to nutrient availability. Overall design: Wildtype and rel deletion mutant (Delta rel) bacteria were grown statically in BHI broth at 37C in an atmosphere of 5% CO2. Cultures were divided in two upon reaching a density of OD620 ~0.1, and lithium mupirocin was added to one culture (t=0) to a final concentration of 100 ng per mL. Treated and untreated cultures were harvested after 20 min further incubation and RNA was extracted by a hot lysis-acid phenol protocol. We performed the following comparisons: Wildtype + mupirocin versus Wildtype untreated (reference); Delta rel + mupirocin versus Delta rel untreated (reference); Delta rel untreated versus Wildtype untreated (reference); Delta rel + mupirocin versus Wildtype + mupirocin (reference). For each comparison, microarray data were obtained from three independent biological replicates and included one dye swap.