Project description:The suceptibility of T. whipplei to doxycycline was investigated at the transcriptional level using a whole-genome DNA microarray. The microarray data showed good agreement with real-time quantitative PCR (R = 0.969). Exposure of T. whipplei with the subinhibitory concentration of doxycycline allowed to observe antibiotic-specific primary expression profiles, while indirect effects were detected with a 10 times higher concencentration. In contrast to what was observed for several microorganisms exposed to antibiotics, the heat-shock proteins were not affected by the exposure of T. whipplei to doxycycline. Consistent with the mode of action of this translation inhibitor, genes encoding for ribosomal proteins and translation factors were differentially transcribed. This analysis also evidenced the regulation of genes that should account for the cell growth arrest. Long-term survival of nonreplicating bacteria is likely to be ensured by an increased level of ppGpp, the nucleotide effector of the stringent response. Gene expression profile to the higher concentrations of doxycycline was mainly characterized by the up-regulation of ABC transporters that possibly form efflux and detoxification systems, through which T. whipplei may limit the effects of this bacteriostatic compound. This work represents the first comprehensive genomic approach providing insight into the expression signature triggered by the exposure of this bacterial pathogen to antibiotics. Keywords: Antibiotic stress with Doxycycline
Project description:Microarray analysis of the global gene expression patterns of Tropheryma whipplei in response to thermal stresses showed unique transcription profiles. A few genes were regulated after 15 min exposure at 43°C, including the dnaK regulon composed of grpE, hspR, dnaK, clpB, cbpA as well as the TWT745 ORFan gene which might encode for another heat-shock protein. This operon is likely to be regulated by two HspR associated inverted repeats (HAIR motifs) found within its 5' region. Putative virulence factors like RibC and IspDF proteins were also up-regulated under such conditions. In contrast to the heat-shock response, T. whipplei transcriptome was strongly modified following cold shock at 4°C. From the 149 genes differentially transcribed, 9 regulons were evidenced, one of them being composed of 5 genes sharing similarities with ABC transporters. Up-regulation of the latter suggests an increase of nutrient uptake during cold stress. As evoked for several bacteria species, the major classes of differentially transcribed genes encode membrane proteins and enzymes involved in fatty acid biosynthesis, indicating that membrane modifications are essential. A most specific feature observed following T. whipplei in response to cold was the up-regulation of heat-shock proteins namely GroEL2 and ClpP1, as well as several genes involved in energy metabolism. All together, these data show that T. whipplei exhibits a specific adaptative response to thermic stresses which fits well to its putative environmental origin. Keywords: thermal stresses responses