The Complex Flagellar Torque Generator of Pseudomonas aeruginosa

Abstract

Flagella act as semirigid helical propellers that are powered by reversible rotary motors. Two membrane proteins, MotA and MotB, function as a complex that acts as the stator and generates the torque that drives rotation. The genome sequence of Pseudomonas aeruginosa PAO1 contains dual sets of motA and motB genes, PA1460-PA1461 (motAB) and PA4954-PA4953 (motCD), as well as another gene, motY (PA3526), which is known to be required for motor function in some bacteria. Here, we show that these five genes contribute to motility. Loss of function of either motAB-like locus was dispensable for translocation in aqueous environments. However, swimming could be entirely eliminated by introduction of combinations of mutations in the two motAB-encoding regions. Mutation of both genes encoding the MotA homologs or MotB homologs was sufficient to abolish motility. Mutants carrying double mutations in nonequivalent genes (i.e., motA motD or motB motC) retained motility, indicating that noncognate components can function together. motY appears to be required for motAB function. The combination of motY and motCD mutations rendered the cells nonmotile. Loss of function of motAB, motY, or motAB motY produced similar phenotypes; although the swimming speed was only reduced to ϳ85% of the wild-type speed, translocation in semisolid motility agar and swarming on the surface of solidified agar were severely impeded. Thus, the flagellar motor of P. aeruginosa represents a more complex configuration than the configuration that has been studied in other bacteria, and it enables efficient movement under different circumstances.

Aeromonas hydrophila motY is essential for polar flagellum function, and requires coordinate expression of motX and Pom proteins

“…Since MotY homologues are also reported to form part of certain proton-driven flagella systems, such as the lateral flagella of Vibrio spp. and the polar flagellum of S. oneidensis and P. aeruginosa (Stewart & McCarter, 2003;Doyle et al, 2004;Paulick et al, 2009), we investigated whether Aeromonas MotY was involved in polar/lateral flagella rotation. By using a motY mutant and a double mutant lafK-motY, we were able to demonstrate that MotY is only essential for A. hydrophila polar flagellum rotation in the presence of MotX.…”

“…Thus, P. aeruginosa PAO1 harbours MotAB and MotCD, which power a single polar flagellum by an unknown mechanism (Doyle et al, 2004;Toutain et al, 2005), while B. subtilis and S. oneidensis MR-1 harbour stator complexes with different ion specificities (Ito et al, 2004;Paulick et al, 2009). B. subtilis MotAB and S. oneidensis MotAB-MotXY are proton-driven, whereas B. subtilis MotPS and S. oneidensis PomAB-MotXY are sodium-driven.…”

A 3D Motile Rod-Shaped Monotrichous Bacterial Model

“…The study of peritrichously flagellated bacteria such as E. coli has received considerable attention [31,12,68,13,24,14,15,74,16,76,79,29]. However, many bacterial strains such as Pseudomonas aeruginosa have a single flagellum at one end of a rodshaped body or a pair of flagella, one at each end [91,39]. Pseudomonas aeruginosa is commonly seen in nosocomial and urinary tract infections and in cystic fibrosis and can have considerable antibiotic resistance [94,30].…”

The Flagellar Basal Body-Associated Protein FlgT Is Essential for a Novel Ring Structure in the Sodium-Driven Vibrio Motor

“…Pseudomonas spp. have only MotY but not MotX; MotY is required for flagellar rotation (12). In Vibrio alginolyticus it has been shown that MotX and MotY are produced as precursor proteins with signal sequences and are translocated to the periplasmic space by a general secretion pathway (35).…”