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Catabolite Repression of Escherichia coli Biofilm Formation. Debra W. Jackson, 2002.Biofilm formation was repressed by glucose in several species of Enterobacteriaceae . In Escherichia coli, this effect was mediated at least in part by cyclic AMP (cAMP)-cAMP receptor protein . A temporal role for cAMP in biofilm development was indicated by the finding that glucose addition after  24 h failed to repress and generally activated biofilm formation .
Identification of a Helix-Turn-Helix Motif of Bacillus thermoglucosidasius HrcA Essential for Binding to the CIRCE Element and Thermostability of the HrcA-CIRCE Complex, Indicating a Role as a Thermosensor. Masafumi Hitomi, 2003.In the heat shock response of bacillary cells, HrcA repressor proteins negatively control the expression of the major heat shock genes, the groE and dnaK operons, by binding the CIRCE (controlling inverted repeat of chaperone expression) element . Studies on two critical but yet unresolved issues related to the structure and function of HrcA were performed using mainly the HrcA from the obligate thermophile Bacillus thermoglucosidasius KP1006 . These two critical issues are (i) identifying the region at which HrcA binds to the CIRCE element and (ii) determining whether HrcA can play the role of a thermosensor . We identified the position of a helix-turn-helix (HTH) motif in B . thermoglucosidasius HrcA, which is typical of DNA-binding proteins, and indicated that two residues in the HTH motif are crucial for the binding of HrcA to the CIRCE element . Furthermore, we compared the thermostabilities of the HrcA-CIRCE complexes derived from Bacillus subtilis and B . thermoglucosidasius, which grow at vastly different ranges of temperature . The thermostability profiles of their HrcA-CIRCE complexes were quite consistent with the difference in the growth temperatures of B . thermoglucosidasius and B . subtilis and, thus, suggested that HrcA can function as a thermosensor to detect temperature changes in cells .
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