Unknown,Transcriptomics,Genomics,Proteomics

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Inducible expression of macrolide efflux in Streptococcus pneumoniae is controlled by transcriptional attenuation of the mef(E)/mel operon

ABSTRACT: Macrolide resistance, increasingly identified in Streptococcus pneumoniae and a wide range of other Gram-positive bacteria, is often due to efflux pumps encoded by the mef/mel(msr) operon found on discrete mobile genetic elements. The regulation of mef/mel(msr) in these elements is not well understood. We defined the promoter controlling the mef(E)/mel operon in S. pneumoniae, identified cis-acting 5′ regulatory elements and determined the mechanism of macrolide-inducible expression of the efflux pump. The mef(E)/mel transcriptional start site was a guanine 327 bp upstream of the mef(E) start codon. Consensus pneumococcal promoter -10 (5′-TATACT-3′) and -35 (5′-TTGAAC-3′) boxes separated by a 17 bp spacer were identified 7 bp upstream of the start site. Analysis of the predicted secondary structure of the 327 bp 5’ region identified four pairs of inverted repeats R1-R8 predicted to fold into stem-loops, a small leader peptide (MTASMRLR) required for macrolide induction and a Rho-independent transcription terminator involving the R5/R6 stem loop. Mutational analyses of the regulatory region identified transcriptional attenuation as the model for the inducible expression of macrolide efflux, which was confirmed by RNA-Seq expression data. The 327 bp region 5’ of mef(E) was highly conserved in other mef/mel(msr)-containing genetic elements complexes including Tn1207.1 and the 5612IQ complex in pneumococci and Tn1207.3 in Group A streptococci. Induction of the mef(E)/mel operon and macrolide efflux occurs by anti-attenuation in the presence of inducing macrolides and appears to be a mechanism RNA-seq was performed on wild type and mutant cultures of four strains of Streptococcus pneumoniae untreated, or treated with spiramycin, LL-37 or erythromycin

ORGANISM(S): Streptococcus pneumoniae

SUBMITTER: Hervé Tettelin

PROVIDER: E-GEOD-54176 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Campylobacter, a major foodborne pathogen, is increasingly resistant to macrolide antibibotics. Previous findings suggeted that development of macrolide resistance in campylobacter requires a multi-step process, but the molecular mechanisms involved in the process are not known. In our study, multiple series of macrolide-resistant C. jejuni mutants were selected in vitro by stepwise exposure of C. jejuni NCTC11168 to increasing concentrations of erythromycin and tylosin. A set of the selected resistance were subjected to microarray and the the global transcriptional profile was analyzed. In this sery, DNA microarray was used to compare the gene expression profiles of macrolide resistant strains (68E1, 68E8 and 68E64) with its parent wild-type strain NCTC11168. The assay identified a small number of genes that showed significant changes (q-value<0.1) in expression in the low-level macrolide resistant strain 68E1, while a large number of gene showing significant changes in intermedia-level resistant stran 68E8 and high-level resistant strain 68 E64. The up-regulated genes in the resistant strains are involved in miscellaneous periplasmic proteins, efflux protienand putative aminotransferase, while the majority of the down-regulated genes are involved in electron transport,lipoprotein, heat shock protein and unknown function proteins. These findings suggest that there is not much change in low-level macrolide resistant C. jejuni strain. The over-expression of efflux pump and periplasmic protein was involved in the development of resistance to macrolide in C. jejuni. Keywords: macrolide resistant C. jejuni selected from NCTC 11168 step-wise selection. The design utilized an available two color microarray slide for the entire transcriptome of Campylobacter jejuni. Four hybridizations were performed each with independently extracted samples of either macrolide susceptible C. jejuni NCTC11168 cDNA samples or macrolide resistant C.jejuni cDNA samples. A dye swap was utilized to help minimize dye dependent bias. Thus, there were four biological replicates of each sample.

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Inducible expression of macrolide efflux in Streptococcus pneumoniae is controlled by transcriptional attenuation of the mef(E)/mel operon

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