Altered motility of Caulobacter Crescentus in viscous and viscoelastic media

Abstract

BackgroundMotility of flagellated bacteria depends crucially on their organelles such as flagella and pili, as well as physical properties of the external medium, such as viscosity and matrix elasticity. We studied the motility of wild-type and two mutant strains of Caulobacter crescentus swarmer cells in two different types of media: a viscous and hyperosmotic glycerol-growth medium mixture and a viscoelastic growth medium, containing polyethylene glycol or polyethylene oxide of different defined sizes.ResultsFor all three strains in the medium containing glycerol, we found linear drops in percentage of motile cells and decreases in speed of those that remained motile to be inversely proportional to viscosity. The majority of immobilized cells lost viability, evidenced by their membrane leakage. In the viscoelastic media, we found less loss of motility and attenuated decrease of swimming speed at shear viscosity values comparable to the viscous medium. In both types of media, we found more severe loss in percentage of motile cells of wild-type than the mutants without pili, indicating that the interference of pili with flagellated motility is aggravated by increased viscosity. However, we found no difference in swimming speed among all three strains under all test conditions for the cells that remained motile. Finally, the viscoelastic medium caused no significant change in intervals between flagellar motor switches unless the motor stalled.ConclusionHyperosmotic effect causes loss of motility and cell death. Addition of polymers into the cell medium also causes loss of motility due to increased shear viscosity, but the majority of immobilized bacteria remain viable. Both viscous and viscoelastic media alter the motility of flagellated bacteria without affecting the internal regulation of their motor switching behavior.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0322-3) contains supplementary material, which is available to authorized users.

Diverse high-torque bacterial flagellar motors assemble wider stator rings using a conserved protein scaffold

“…Salmonella WT: EMD-3154; Vibrio fischeri WT: EMD-3155; Campylobacter jejuni WT: EMD-3150; V. fischeri motB: EMD-3156; C. jejuni motB: EMD-3157; C. jejuni flgQ: EMD-3158; C. jejuni flgP: EMD-3159; C. jejuni pflA: EMD-3160; C. jejuni pflB: EMD-3161; and V. fischeri flgP: EMD-3162). 1 To whom correspondence may be addressed. Email: mbeeby@imperial.ac.uk or david.…”

“…However, a diverse spectrum of flagellar swimming ability is seen across the bacterial kingdom. Caulobacter crescentus inhabits low-nutrient freshwater environments where it swims using a high-efficiency flagellar motor (1,2), whereas Vibrio species produce high-speed, sodium-driven polar flagella to capitalize on the high sodium gradient of their marine habitat (3). On the other hand, the e-proteobacteria and spirochetes, many of which thrive exclusively in association with a host, have evolved characteristically rapid and powerful swimming capabilities that enable them to bore through mucous layers coating epithelial cells or between tissues.…”

Influence of Physical Effects on the Swarming Motility of Pseudomonas aeruginosa

“…372773, PEO 400,000; Sigma-Aldrich, St. Louis, MO). Its viscosity and osmolarity have been characterized and reported in a previous work (44).…”

Upstream Swimming in Microbiological Flows

“…Despite the widespread implications of viscoelastic effects on biological processes, research on motile microorganism dynamics in confined environments is largely limited to Newtonian fluids [15][16][17][18][19][20][21][22][23][24][25]. Recently, a large number of studies have considered locomotion in quiescent non-Newtonian fluids at the scale of microswimmers, in experiment, simulations and theory [26][27][28][29][30][31][32][33], but little is known about the dynamical behaviour of swimmers subject to large-scale non-Newtonian flows.…”

“…Therefore, changes in the swimming speed due to viscoelasticity, as studied in Refs. [26][27][28][29][30][31][32][33], are readily incorporated in this model.…”