Number of genes up- (green) and down- (red) regulated in <i>S</i>. Typhimurium under acid and heat stressing conditions and immediately and 30 min after removing the stressing conditions.

<p>Few genes were affected by acid stress (A) while transcription of a large number of genes was altered under heat stress (B). Majority of up-regulated genes under heat stress remained up-regulated 30 minutes after stress condition ceased. Black numbers and solid lines show up- and down- regulated genes maintained throughout the experiment.