Time series (T= 0-4 hours) for E. coli K-12 MC4100 after a shift from 23˚C to 37˚C (M9 minimal glycerol medium, exponential phase growth)

We investigated the effect of a temperature shift from 23˚C to 37˚C, mimicking the temperature transition experienced by a microbe as it enters a human host. This strategy allowed the exploration of the kinetics of gene expression changes in immediate response to a temperature upshift and to characterize the suite of genes required to respond to 37˚C in the first few hours. We demonstrate that a significant number of genes are rapidly altered in expression within minutes to hours after a temperature shift. Some are only induced transiently, while are required for long-term adaptation. Many of these genes are related to metabolism, stress response, and immune evasion suggesting that temperature may serve as a sentinel cue to predict and prepare for niche adaptation in the host. An aerobic, mid-exponential phase (A600= 0.2-0.6) culture was grown at 23˚C in M9 minimal medium containing glycerol as a carbon source. Aliquots of the initial culture were shifted to 37˚C to allow harvest of cells at time points after a shift to 37˚C. Microarray results compare each timepoint after the shift to 37˚C (T= 0.5, 1, or 4 hours) to the initial T=0 timepoint grown at 23˚C.