Transcriptome analysis of Escherichia coli O157:H7 EDL933 during heat shock.

The response to elevated temperature [heat shock (HS)] is highly conserved. The transcriptome of Escherichia coli K-12 has been studied under a variety of conditions while such studies involving E. coli O157:H7 are only now being conducted. To better understand the impact of HS on E. coli O157:H7, global transcript levels of strain EDL933 cells shifted from 37 to 50 degrees C for 15 min were compared with cells held at 37 degrees C by microarray. Using a mixed model analysis, 193 genes were found to be differentially transcribed at P<0.0042 with a q value <0.1. The 111 downregulated genes include the curli pili-associated genes csgABCDEFG, maltose transport-associated proteins malEFK, and NADH dehydrogenase subunit encoding nuoCEHIJN. The 82 genes upregulated include the HS-induced genes rpoH, dnaK, dnaJ, groEL, groES, and grpE along with two LEE-encoded genes: hypothetical gene Z5121 and sepZ. Twenty-three additional genes located in O-islands were found to be differentially expressed. Quantitative real-time PCR (qRT-PCR) was performed to validate the microarray results. Also, samples subjected to a 30-42 degrees C shift were examined by qRT-PCR to confirm differential transcription of selected genes. These results indicate that this pathogen may regulate its virulence factors in response to temperature changes.