Inter- and intraserotypic variation in theStreptococcus pyogenesRgg regulon

Abstract

Human isolates of Streptococcus pyogenes, a Gram-positive bacterium, are characterized by significant genetic and phenotypic variation. The rgg locus, also known as ropB, is a global transcriptional regulator of genes associated with metabolism, stress responses, and virulence in S. pyogenes strain NZ131 (serotype M49). To assess the breadth of the Rgg regulon, the rgg gene was inactivated in three additional strains representing serotypes M1 (strains SF370 and MGAS5005) and M49 (strain CS101). Changes in gene expression were identified in the post-exponential phase of growth using Affymetrix NimbleExpress Arrays. The results identified an Rgg core-regulon consisting of speB and adjacent hypothetical protein gene, spy2040, and a variable and strain-specific sub-regulon, ranging in size from a single gene (spy1793) in strain MGAS5005 to 43 genes in strain SF370. Thus, both interserotypic and intraserotypic variation is characteristic of the Rgg regulon in S. pyogenes.

Naturally occurring single amino acid replacements in a regulatory protein alter streptococcal gene expression and virulence in mice

“…We used non-polar insertional mutagenesis to replace nearly the entire ropB gene in strain MGAS10870 and strain MGAS9937 with a spectinomycin resistance cassette to create strains 10870ΔropB and 9937ΔropB (see Supplemental Figure 1 for confirmatory Southern blot analysis). Consistent with other reports regarding insertional inactivation of ropB (29,32,37,38), we found no significant difference in growth in THY between the parental and isogenic mutant strains ( Figure 5A). …”

“…The importance of the choice of the parental strain to study RopB inactivation was clearly demonstrated by the markedly different size of the RopB transcriptome in strains MGAS10870 and MGAS9937 ( Figure 5). Our finding that a SNP can be associated with significant differences in the breadth of the RopB transcriptome provides a potential explanation for previous observations regarding marked strain-to-strain variation in the effect of RopB inactivation on group A streptococcal global gene expression (37).…”

“…Conversely, strains RopB-V7I and RopB-C85Y had similar characteristics to the parental strain MGAS10870 ( Figure 6). In some group A streptococci, RopB negatively influences the expression of slo, which encodes the streptolysin O cytotoxin (25,32,37,47). In contrast to the differences observed in speB transcript level, there was no statistically significant difference in slo transcript between MGAS10870 and any of the RopB-altered strains ( Figure 6E).…”

“…There are several key virulence factors influenced by RopB, including the secreted cysteine protease SpeB ( Figure 5 and refs. 29,37). Our phylogenetic analysis indicated that group A streptococci isolated from the highest numbers of patients are those with a wild-type RopB and those with RopB variants that reduce but do not eliminate SpeB production (Table 1 and Figure 4).…”

“…One key question regarding RopB function is why inactivation of ropB in different group A streptococci has markedly different effects on global gene expression. For example, study of 2 serotype M1 strains found that the RopB-controlled transcriptome consisted of 43 genes in 1 strain but only 3 genes in the other strain (37). To test the hypothesis that RopB amino acid polymorphisms influence the RopB transcriptome, we compared the RopB transcriptome in strain MGAS10870 (ropB1 allele) and strain MGAS9937 (ropB4 allele encoding the C85Y RopB variant).…”