Transcriptome comparison of S. pyogenes strains MGAS2221 and 2221ΔrivRX. Streptococcus pyogenes

The rivR gene encodes a putative transcriptional regulator, while the rivX gene encodes a putative small regulatory RNA. To determine the RivRX regulon during exponential phase growth in THY broth we compared parental strain MGAS2221 with isogenic rivRX mutant strain 2221ΔrivRX. Overall design: GAS strains were grown in THY broth to mid-exponential phase, corresponding to an O.D.600 of 0.5. A 4.5ml aliquot of each GAS culture was added to 9ml of RNAprotect (Qiagen Inc.). Following addition of RNAprotect, samples were incubated at room temperature for 5 mins before centrifuging. Supernatant was removed and the pellets quick frozen in liquid nitrogen and stored at -80 °C until ready to use. RNA isolation, cDNA synthesis, and use of our custom Affymetrix microarray was as previously described (Perez et al., 2009)