Effects of glycosylation on swimming ability and flagellar polymorphic transformation in Pseudomonas syringae pv. tabaci 6605

Abstract

The role of flagellin glycosylation on motility was investigated in Pseudomonas syringae pv. tabaci. The swimming activity of glycosylation-defective mutants was prominently decreased in a highly viscous medium. The mutants showed differences in polymorphic transitions and in the bundle formation of flagella, indicating that glycosylation stabilizes the filament structure and lubricates the rotation of the bundle.

FIG. 1.

Two-night culture of the WT, the fgt1-deleted mutant (Δfgt1), and six-serine-replacement mutants (6 S/A). Bacterial strains were incubated in LB supplemented with 10 mM MgCl₂ for 24 h at 25°C with agitation and then for 20 h without agitation.

FIG. 2.

(A) Effect of viscosity on swimming motility of the WT and glycosylation-defective mutants (Δfgt1, fgt2-deleted mutant [Δfgt2], 6 S/A, and six mutants replacing a single Ser with Ala [S143A, S164A, S173A, S183A, S193A, and S201A]) from P. syringae pv. tabaci 6605. The percentage of swimming cells is indicated for each. Viscosity was increased by the addition of PVP. (B) Effect of viscosity on swimming speed of the WT and glycosylation-defective mutants from P. syringae pv. tabaci 6605.

FIG. 3.

Polymorphic transitions of flagellar filaments from the WT and glycosylation-defective mutants of P. syringae pv. tabaci 6605. (A) Dark-field light micrographs of flagella. Typical images of Coiled, Semi-Coiled, and a mixture of Semi-Coiled and Normal filaments prepared from the WT and undulant filaments prepared from Δfgt1 and 6 S/A mutant strains. (B) Phase diagrams of polymorphs by pH and NaCl concentration. SC, Semi-Coiled; No, Normal; Co, Coiled; St, Straight; DP, depolymerized.

FIG. 4.

Bundle formation of flagella from glycosylation-defective mutants. (A) Bundle formation of flagella in swimming bacteria (the WT and Δfgt1 and 6 S/A mutants) under a dark-field microscope. (B) Electron micrographs of each strain. Insets are magnifications of the entangled flagella.