Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

5448 vs 5448R- in vivo 24h

ABSTRACT: Microarray analysis was performed on in vivo-derived RNA from the well characterized GAS strain 5448 and its derivative 5448R-, containing the mutated ropB allele from 5628. We followed a cyclic design that allowed us to compare every condition to each other at least twice, and guaranteed dye swapping to eliminate effects of non-specific binding. This study consists of 4 replicates of 5448 and 3 replicates of 5448R-.

ORGANISM(S): Streptococcus pyogenes

SUBMITTER: Andrew Hollands

PROVIDER: E-GEOD-13656 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

A naturally occurring mutation in ropB suppresses SpeB expression and reduces M1T1 group A streptococcal systemic virulence.

Hollands Andrew A Aziz Ramy K RK Kansal Rita R Kotb Malak M Nizet Victor V Walker Mark J MJ

PloS one 20081231 12

Epidemiological studies of group A streptococcus (GAS) have noted an inverse relationship between SpeB expression and invasive disease. However, the role of SpeB in the course of infection is still unclear. In this study we utilize a SpeB-negative M1T1 clinical isolate, 5628, with a naturally occurring mutation in the gene encoding the regulator RopB, to elucidate the role of RopB and SpeB in systemic virulence. Allelic exchange mutagenesis was used to replace the mutated ropB allele in 5628 wit ...[more]

PMID: 19116661

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Project description:Background Small colony variants (SCVs) are slow-growing bacteria, which often show increased resistance to antibiotics and cause latent or recurrent infections. It is therefore important to understand the mechanisms at the basis of this phenotypic switch. Methodology/Principal findings One SCV (termed PAO-SCV) was isolated, showing high resistance to gentamicin and to the cephalosporine cefotaxime. PAO-SCV was prone to reversion as evidenced by emergence of large colonies with a frequency of 10-5 on media without antibiotics while it was stably maintained in presence of gentamicin. PAO-SCV showed a delayed growth, defective motility, and strongly reduced levels of the quorum sensing Pseudomonas quinolone signal (PQS). Whole genome expression analysis further suggested a multi-layered antibiotic resistance mechanism, including simultaneous over-expression of two drug efflux pumps (MexAB-OprM, MexXY-OprM), the LPS modification operon arnBCADTEF, and the PhoP-PhoQ two-component system. Conversely, the genes for the synthesis of PQS were strongly down-regulated in PAOSCV. Finally, genomic analysis revealed the presence of mutations in phoP and phoQ genes as well as in the mexZ gene encoding a repressor of the mexXY and mexABoprM genes. Only one mutation occurred only in REV, at nucleotide 1020 of the tufA gene, a paralog of tufB, both encoding the elongation factor Tu, causing a change of the rarely used aspartic acid codon GAU to the more common GAC, possibly causing an increase of tufA mRNA translation. High expression of phoP and phoQ was confirmed for the SCV variant while the revertant showed expression levels reduced to wild-type levels. Conclusions By combining data coming from phenotypic, gene expression and proteome analysis, we could demonstrate that resistance to aminoglycosides in one SCV mutant is multifactorial including overexpression of efflux mechanisms, LPS modification and is accompanied by a drastic down-regulation of the Pseudomonas quinolone signal quorum sensing system. We used microarrays to study changes in gene expression during early and late stationary phase of SCV and WT strains. SCV and WT cultures were grown in triplicate until early (24h) and late (48h) stationary phase. RNA was extracted, labelled and hybridised on Affymetrix P. aeruginosa expression microarrays.

Dataset Information

5448 vs 5448R- in vivo 24h

Publications

A naturally occurring mutation in ropB suppresses SpeB expression and reduces M1T1 group A streptococcal systemic virulence.

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