Regulation of the Swarming Inhibitor disA in Proteus mirabilis

Abstract

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 FlhD 4 C 2 , the class I flagellar master regulator, did not have a role in disA regulation. The putative product of DisA, phenethylamine, was able to inhibit disA expression, indicating that a negative regulatory feedback loop was present. Transposon mutagenesis was used to identify regulators of disA and revealed that umoB (igaA) was a negative regulator of disA. Our data demonstrate that the regulation of disA by UmoB is mediated through the Rcs phosphorelay. Proteus mirabilis is a Gram-negative bacillus and a causative agent of urinary tract infections in patients with abnormal urethras or requiring long-term catheterization (1, 2, 3). P. mirabilis is also known for its ability to swarm, a form of flagellummediated 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 vegetative swimming cells differentiate into elongated, multinucleate, aseptate, hyperflagellated swarmer cells, as reviewed in reference 6. The swarmer cells aggregate to form multicellular rafts and move concentrically away from the central inoculum for approximately 1 to 2 h before dedifferentiating back to vegetative swimming cells (7). This cycle of differentiation and consolidation gives P. mirabilis its characteristic bull's-eye appearance on agar plates (4).Flagellar biogenesis is tightly controlled in P. mirabilis through a hierarchically tiered regulatory cascade consisting of class I, II, and III gene clusters (reviewed in reference 8). Class I consists solely of the flagellar master regulator flhDC. The FlhD 4 C 2 heterohexamer is the master swarming regulator and activates transcription of class II genes (9, 10, 11). Class II is comprised of genes needed to form the hook-basal body structure of the flagella as well as fliA, encoding the swarming sigma factor 28 , and flgM, the corresponding anti-sigma factor.28 is responsible for transcribing class III genes, including genes involved in chemotaxis, and the structural genes of the flagellar filament and motor. The energy expenditure to fully flagellate a swarmer cell and the cyclic aspect of swarming require that swarming be a tightly regulated process. Several signals inducing differentiation, such as the inhibition of flagellar rotation, accumulation of putrescine, and O-antigen contact with a solid surface, have been identified; however, the signals responsible for consolidation are poorly understood (12,13,14,15).A novel regulator of swarming, disA, that bears homology to aromatic amino acid decarboxylases was discovered by Stevenson et al. (16). Disruption of the disA gene resulted in a hyperswarming phenotype, whereas overexpression completely abolished swarming (16). Currently, the mechanism by whic...

Proteus mirabilisand Urinary Tract Infections

“…DisA is predicted to be an amino acid decarboxylase. Addition of the decarboxylated amino acid phenethylamine reduced both swarming and disA expression (97, 98). Phenethylamine also inhibited transcription of class 2 and 3 flagellar genes yet had a minimal effect on flhDC .…”

“…The Rcs phophorelay (reviewed in (104)) has been implicated in swarming by P. mirabilis and is discussed below. In P. mirabilis , UmoB is a negative regulator of swarming inhibitor disA (discussed above) (98). …”

Proteus mirabilisand Urinary Tract Infections

“…The Rcs phophorelay (reviewed in (104)) has been implicated in swarming by P. mirabilis and is discussed below. In P. mirabilis, UmoB is a negative regulator of swarming inhibitor disA (discussed above) (98).…”

Augmented Enterocyte Damage During Candida albicans and Proteus mirabilis Coinfection

“…How expression of the Proteus hemolysin HpmA and the facilitator protein HpmB is regulated, is only incompletely understood, but it is linked to swarming. Swarming is typically observed on solid surfaces and it requires the differentiation of rod-shaped vegetative cells (also called swimmers) into elongated hyperflagellated swarm cells ( Belas and Suvanasuthi, 2005 ; Szostek and Rather, 2013 ; Tuson et al., 2013 ; Little et al., 2019 ). It is associated with increased expression of virulence effectors, including hemolysin ( Allison et al., 1992b ; Gygi et al., 1995 ; Liaw et al., 2000 ; Fraser et al., 2002 ; Jones et al., 2004 ; Belas and Suvanasuthi, 2005 ; Wang et al., 2006 ).…”