Aggregation Temperature of Escherichia coli Depends on Steepness of the Thermal Gradient.Bacterial chemotaxis, the directed migration of bacteria in a gradient of chemoattractant, is one of the most well-studied and well-understood processes in cell biology.  On the other hand, bacterial thermotaxis, the directed migration of bacteria in a gradient of temperature, is understood relatively poorly, with somewhat conflicting reports by different groups.  One of the reasons for that is the relative technical difficulty of the generation of well-defined gradients of temperature that are sufficiently steep to elicit readily detectable thermotaxis.  Here, we used a specially designed microfluidic device to study thermotaxis of Escherichia coli in a broad range of thermal gradients with a high rate of data collection.  Our experiments also highlight the fact that assessments of thermal gradients by changes in fluorescence of temperature-sensitive fluorescent dyes need to account for thermophoresis of the dyes.
THERM