Transcriptional silencing and thermoregulation of gene expression in Escherichia coli.

Expression of specific adhesive properties by bacteria in general seems to be regulated to fit the environmental conditions. An example is the transcriptional regulation of digalactoside-specific binding by uropathogenic strains of Escherichia coli. The fimbrial structures (pili) on the bacterial surface carry the adhesin and are present during growth at 37 degrees C but are not produced by cells at lower temperatures, such as 25 degrees C. Thermoregulation of expression is due to temperature-dependent transcription of a regulatory cistron in the pilus-adhesin gene cluster. We have now identified and characterized a new regulatory locus (drdX) and show that a histone-like bacterial protein has an important role in this novel example of thermoregulation of transcription.