Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Adaptation of group A Streptococcus to human amniotic fluid

ABSTRACT: Background. For more than 100 years, group A Streptococcus has been identified as a cause of severe, and in many cases fatal, infections of the female urogenital tract. Due to advances in hospital hygiene and the advent of antibiotics, this type of infection has been virtually eradicated. However, within the last three decades there has been an increase in severe intra- and post-partum infections attributed to GAS. Principal Findings. The majority of changes in the GAS transcriptome involved down regulation of multiple adhesins and virulence factors and activation of the stress response. We observed significant changes in genes involved in the arginine deiminase pathway and in the nucleotide de novo synthesis pathway. Conclusions/Significance. Our work provides new insight into how pathogenic bacteria respond to their environment to establish infection and cause disease. To identify genes that were up or down regulated in response to growth in AF, GAS was grown in human AF or standard laboratory media (THY) and samples for expression microarray analysis were collected during mid-logarithmic, late-logarithmic, and stationary growth phases. Microarray analysis was performed using a custom Affymetrix chip and normalized hybridization values derived from three biological replicates were collected at each growth point. Ratios of AF/THY above a 2-fold change and P-value < 0.05 were considered significant.

ORGANISM(S): Streptococcus pyogenes MGAS6180

SUBMITTER: Ann Bongiovanni

PROVIDER: E-GEOD-19985 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Recent whole-genome sequencing of large populations of the same bacterial species has revealed significant disparity among genes in the frequency of single nucleotide polymorphisms (SNPs). For example, a previous analysis of invasive serotype M3 group A streptococci (GAS) found the highest frequency of SNPs in the gene (ropB) encoding the regulator of proteinase B (RopB). This finding led us to hypothesize that RopB polymorphisms contribute to altered GAS host-pathogen interactions. Sequencing of ropB in 171 invasive serotype M3 GAS strains from a surveillance study identified 19 distinct ropB alleles. Inactivation of the ropB gene in strains producing distinct RopB variants had dramatically different effects on GAS global gene expression. Further, analysis of laboratory-generated isoallelic GAS strains differing only by a single amino acid replacement in RopB confirmed that the variant protein affected the transcript level of the gene encoding streptococcal proteinase B, a major RopB-regulated virulence factor. Comparison of parental, RopB-inactivated, and RopB isoallelic strains in mouse infection models demonstrated that RopB polymorphisms significantly influence GAS virulence and disease manifestations. These studies detail a paradigm in which unbiased, whole-genome sequence analysis of populations of clinical bacterial isolates creates new avenues of productive investigation into the pathogenesis of common human infections. This study examined the effects of RopB inactivaiton on two distinct serotype M3 group A streptococcal strains with distinct forms of the RopB protein. RopB was inactivated in a strain with a wild-type RopB allele (strain MGAS10870) and in a strain with a RopB allele containing a C85Y polymorphism (strain MGAS9937). The wild-type and RopB inactivated strains were grown in duplicate to the early stationary growth phase in standard laboratory medium (THY). Total RNA was isolated, converted to cDNA, and hybridized to a custom-made Affymetrix GeneChip.

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Adaptation of group A Streptococcus to human amniotic fluid

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