Inorganic polyphosphate is needed for swimming, swarming, and twitching motilities of Pseudomonas aeruginosa

Abstract

Polyphosphate kinase (PPK), encoded by the ppk gene, is the principal enzyme in many bacteria for the synthesis of inorganic polyphosphate (poly P) from ATP. A knockout mutant in the ppk gene of Pseudomonas aeruginosa PAO1 is impaired in flagellar swimming motility on semisolid agar plates. The mutant is deficient in type IV pili-mediated twitching motility and in a ''swarming motility'' previously unobserved in P. aeruginosa. In swarming cultures, the polar monotrichous bacteria have differentiated into elongated and polar multitrichous cells that navigate the surface of solid media. All of the motility defects in the ppk mutant could be complemented by a plasmid harboring the ppk gene. Because bacterial motility is often crucial for their survival in a natural environment and for systemic infection inside a host, the dependence for motility on PPK reveals important roles for poly P in diverse processes such as biofilm formation, symbiosis, and virulence.I norganic polyphosphate (poly P) is a linear chain of tens or many hundreds of phosphate residues linked by high-energy phosphoanhydride bonds. It is found in every cell in nature: bacterial, archaeal, fungal, protozoan, plant, and animal (1, 2). Poly P has numerous and varied biological functions depending on where it is (species, cell, or subcellular compartment) and when it is needed. Among these functions are substitution for ATP in kinase reactions; reservoir of phosphate; chelation of divalent metals; capsule of bacteria; and regulatory roles in growth, development, stress, and deprivation (1, 2). In our studies of Escherichia coli, the most significant function observed thus far is its regulatory role in adapting to nutritional stringencies and environmental stresses, and for survival in the stationary phase of growth (3). This role has been inferred from the behavior of mutant cells lacking polyphosphate kinase (PPK), the enzyme responsible for the synthesis of poly P from ATP (4).Motility is arguably one of the most impressive features in microbial physiology. Movement in aqueous environments by swimming or along surfaces by using different modes of translocation has been classified into several distinct forms (5). Swimming on a surface takes place when the fluid film is sufficiently thick and the micromorphological pattern is unorganized. When the fluid layer on a surface is relatively thin, the swimming bacteria become elongated and hyperflagellated and move in a coordinated manner known as ''swarming'' (5-7). Twitching motility is another form of translocation on a solid surface in which the micromorphological pattern is less organized than in swarming (5, 8). Among these three modes of surface translocation, swimming and swarming depend on flagella, whereas twitching depends on type IV pili (5).These various forms of surface motility enable bacteria to establish symbiotic and pathogenic associations with plants and animals (9-11). Potential benefits of motility include increased efficiency of nutrient acquisition, avoidance of toxic substances, ab...

Surface-motility induction, attraction and hitchhiking between bacterial species promote dispersal on solid surfaces

“…Such a mode of motility allows bacteria to escape local stresses, translocate to a better nutritional environment and efficiently invade host tissue (Fraser and Hughes, 1999;Rashid and Kornberg, 2000;Harshey, 2003). However, despite the benefits, for many bacterial species the ability to migrate on solid surfaces does not exist or is dependent on high surface wetness and thus, restricted to specific environmental conditions (Wang et al, 2005;Kearns, 2010).…”

Identification of two new genes involved in twitching motility in Pseudomonas aeruginosa

“…These Mu transposon mutants were screened for defects in twitching motility, using the subsurface stab assay. When cells are stabbed through an agar layer to the bottom of the Petri dish, colony expansion at the interstitial surface between the agar and the plastic occurs by twitching motility (Semmler et al, 1999;Rashid & Kornberg, 2000). Eight mutants deficient in twitching motility were isolated, out of approximately 2000 insertion mutants (Fig.…”

Antibiofilm activity substances derived from coral symbiotic bacterial extract inhibit biofouling by the model strain Pseudomonas aeruginosa PAO1

“…Then, this agar was poured immediately over the surface of a solidified LB agar plate as an overlay and allowed to dry for 3 h at 30°C. The plates were then centre point inoculated with PAO1 (1 × 10 7  CFU ml −1 ) and incubated at 37°C for 24 h. The extent of swarming was then determined by measuring the diameter of the motility swarms (Rashid and Kornberg, 2000). …”