Regulation of the Swarming Inhibitor disA in Proteus mirabilis

The disA gene encodes a putative amino acid decarboxylase that inhibits swarming in Proteus mirabilis. 5 = rapid amplification of cDNA ends (RACE) and deletion analysis were used to identify the disA promoter. The use of a disA-lacZ fusion indicated that FlhD4C2, the class I flagellar master regulator, did not have a role in disA regulation. The putative product of DisA, phenethyl-amine, was able to inhibit disA expression, indicating that a negative regulatory feedback loop was present. Transposonmu-tagenesis was used to identify regulators of disA and revealed that umoB (igaA) was a negative regulator of disA. Our data dem-onstrate that the regulation of disA by UmoB is mediated through the Rcs phosphorelay. Proteus mirabilis is a Gram-negative bacillus and a causativeagent of urinary tract infections in patients with abnormal urethras or requiring long-term catheterization (1, 2, 3). P. mira-bilis is also known for its ability to swarm, a form of flagellum-mediated surface motility (4, 5). In liquid medium, P. mirabilis exists as a vegetative, peritrichously flagellated swimming cell. However, 3 to 4 h after being placed on a solid surface, the vege-tative swimming cells differentiate into elongated, multinucleate, aseptate, hyperflagellated swarmer cells, as reviewed in reference 6. The swarmer cells aggregate to form multicellular rafts an