Regulation of flhDC expression in Proteus mirabilis

Area of Science:

• Microbiology
• Bacterial Motility
• Gene Regulation

Background:

• The flhDC operon is a master regulator of flagellar synthesis and motility in many bacteria.
• Understanding flhDC regulation is crucial for controlling bacterial behavior, including swarming motility.

Purpose of the Study:

• To investigate the impact of upstream regulatory elements on flhDC expression and swarming behavior in Proteus mirabilis.
• To identify potential repressor proteins controlling flhDC transcription.

Main Methods:

• Generating transposon insertion mutants in the upstream region of the flhDC operon.
• Analyzing swarming initiation, velocity, and pattern formation on solid media.
• Quantifying flhDC mRNA levels using Northern blotting.
• Creating targeted gene disruptions in putative repressor genes (rcsB, ompR, lrhA, hdfR).

Main Results:

• Transposon insertions upstream of flhDC enhanced swarming initiation and velocity (2-2.5 fold).
• Mutants exhibited defects in cellular consolidation and failed to form typical swarming rings.
• Increased flhDC mRNA levels were observed in mutants, correlating with enhanced swarming.
• Disruption of rcsB significantly increased swarming and flhDC mRNA accumulation, suggesting a repressor role.

Conclusions:

• Upstream regulatory regions of flhDC play a critical role in modulating swarming motility in P. mirabilis.
• RcsB acts as a repressor of flhDC transcription, influencing both swarming and cellular differentiation.
• Novel regulatory mechanisms for flhDC control swarming behavior and pattern formation.