Novel Regulators of the flhDC Gene Encoding the Flagella Master Regulator in Escherichia Coli K-12.

Escherichia coli possesses the ability to perceive diverse environmental conditions and regulate its gene expression in flagellar formation. In E. coli, the FlhDC complex serves as a pivotal element initiating the construction of the hook-basal body structure, a critical component in the initial stages of flagellar assembly. Previous research has demonstrated that multiple trans factors influence flhDC expression by responding to environmental cues. In this study, we conducted a promoter-specific transcription factor (PS-TF) screening method with the objective of identifying the complete set of transcription factors involved in the regulation of flhDC expression. The analysis revealed 60 factors (49 with known functions and 11 with unknown functions) that bind to the flhDC promoter. The study concentrated on four factors-ArgR, HupB, IciA, and YdcI-that diminish motility without causing growth inhibition. Notably, YdcI, which is responsive to pH variations, was found to enhance biofilm formation and significantly suppress flhDC expression, particularly under acidic conditions. This finding suggests that YdcI represents a novel regulatory factor influencing both biofilm formation and flagellar suppression.