Transcriptomes of covR/S mutant strains of S. pyogenes

Two covR mutant derivatives of parental strain MGAS2221 were recovered from mice experimentally infected with MGAS2221 and shown to differ in terms of the number and concentration of secreted proteins. One of the covR mutant strains had a secretion phenotype identical to a covS mutant strain, while the other had a secretion phenotype identical to a constructed covR mutant strain. To further investigate the potential differences between the two covR mutant strains we performed expression microarray analysis. Single cultures of each of the four GAS strains tested were grown in THY broth to early exponential phase (O.D. 0.2). Two volumes of RNA protect were added, the samples incubated at room temperature for 5 minutes, and the bacteria collected through centrifugation. Total RNA was isolated via a mechaniscal disruption method, converted to cDNA, fragmented, labeled, and hybridized to our Affymetrix microarray. Estimates of gene expression were calculated using GCOS software v1.4. Data represent probes for serotype M1.