Altered motility of XXXX in viscous and viscoelastic media.

@entity101 @entity653 @entity1319 @entity14273 @entity968
BACKGROUND: Motility 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 @entity14273 swarmer cells in two different types of media: a viscous and hyperosmotic @entity653 -growth medium mixture and a viscoelastic growth medium, containing @entity968 or @entity968 of different defined sizes. RESULTS: For all three strains in the medium containing @entity653 , 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 @entity1319 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. CONCLUSION: Hyperosmotic effect causes @entity1319 and cell death. Addition of polymers into the cell medium also causes @entity1319 due to @entity101 , 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.
