Global Transcriptome Analysis of Tropheryma whipplei in Response to Temperature Stresses

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 4 conditions of temperature 2 biological replicates per condition 1 dye-swap per condition 1 referecne sample per hybridation (37°C Day 28) Controls inculded on microarray and added in each sample before dye-labelling 4 replicates per microarray