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Altered motility of Caulobacter Crescentus in viscous and viscoelastic media.

Gao Y, Neubauer M, Yang A, Johnson N, Morse M, Li G, Tang JX - BMC Microbiol. (2014)

Bottom Line: For 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.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.Hyperosmotic effect causes loss of motility and cell death.

View Article: PubMed Central - PubMed

Affiliation: Physics Department, Brown University, Providence, RI, 02192, USA. yukun_gao@alumni.brown.edu.

ABSTRACT

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 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.

Results: For 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.

Conclusion: Hyperosmotic 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.

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Loss in motility with polymer added into the medium of synchronized SB3860 swarmer cells. A. Fraction of motile cells plotted versus PEG 4000, PEG 35000, and PEO 400000 in weight percentage. B. The same data collapsed to a single line when re-plotted as a function of viscosity. The errors bars, some smaller than the symbols, represent the standard errors of the mean. The numbers of cells counted were 531 in PEG 4000, 5884 in PEG 35000, and 1191 in PEO 400000.
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Fig2: Loss in motility with polymer added into the medium of synchronized SB3860 swarmer cells. A. Fraction of motile cells plotted versus PEG 4000, PEG 35000, and PEO 400000 in weight percentage. B. The same data collapsed to a single line when re-plotted as a function of viscosity. The errors bars, some smaller than the symbols, represent the standard errors of the mean. The numbers of cells counted were 531 in PEG 4000, 5884 in PEG 35000, and 1191 in PEO 400000.

Mentions: In a rich growth medium such as peptone yeast extract (PYE), C. crescentus usually spends around 30 minutes in the swarmer stage of its life cycle, after which it sheds its flagellum, thereby losing its motility [22]. Mixing PEG or PEO with young swarmer cells, we observed slight decreases in the percentage of motile cells. As a function of the polymer concentration, we found the decrease to be highly sensitive to the polymer size. Whereas 0.5% PEO 400000 caused loss of motility by over 50%, 10% PEG 4000 caused only about 10% loss of motility (Figure 2A). This size sensitivity suggests strongly that rheological property of the polymer matrix might be the main cause for the loss of motility. Indeed, when plotting the same data as a function of the measured shear viscosity (listed on Table 1), we found the same gradual drop in motility, with the combined data in solutions of these three polymers collapsing to a single line (Figure 2B).Figure 2


Altered motility of Caulobacter Crescentus in viscous and viscoelastic media.

Gao Y, Neubauer M, Yang A, Johnson N, Morse M, Li G, Tang JX - BMC Microbiol. (2014)

Loss in motility with polymer added into the medium of synchronized SB3860 swarmer cells. A. Fraction of motile cells plotted versus PEG 4000, PEG 35000, and PEO 400000 in weight percentage. B. The same data collapsed to a single line when re-plotted as a function of viscosity. The errors bars, some smaller than the symbols, represent the standard errors of the mean. The numbers of cells counted were 531 in PEG 4000, 5884 in PEG 35000, and 1191 in PEO 400000.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4302598&req=5

Fig2: Loss in motility with polymer added into the medium of synchronized SB3860 swarmer cells. A. Fraction of motile cells plotted versus PEG 4000, PEG 35000, and PEO 400000 in weight percentage. B. The same data collapsed to a single line when re-plotted as a function of viscosity. The errors bars, some smaller than the symbols, represent the standard errors of the mean. The numbers of cells counted were 531 in PEG 4000, 5884 in PEG 35000, and 1191 in PEO 400000.
Mentions: In a rich growth medium such as peptone yeast extract (PYE), C. crescentus usually spends around 30 minutes in the swarmer stage of its life cycle, after which it sheds its flagellum, thereby losing its motility [22]. Mixing PEG or PEO with young swarmer cells, we observed slight decreases in the percentage of motile cells. As a function of the polymer concentration, we found the decrease to be highly sensitive to the polymer size. Whereas 0.5% PEO 400000 caused loss of motility by over 50%, 10% PEG 4000 caused only about 10% loss of motility (Figure 2A). This size sensitivity suggests strongly that rheological property of the polymer matrix might be the main cause for the loss of motility. Indeed, when plotting the same data as a function of the measured shear viscosity (listed on Table 1), we found the same gradual drop in motility, with the combined data in solutions of these three polymers collapsing to a single line (Figure 2B).Figure 2

Bottom Line: For 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.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.Hyperosmotic effect causes loss of motility and cell death.

View Article: PubMed Central - PubMed

Affiliation: Physics Department, Brown University, Providence, RI, 02192, USA. yukun_gao@alumni.brown.edu.

ABSTRACT

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 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.

Results: For 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.

Conclusion: Hyperosmotic 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.

Show MeSH
Related in: MedlinePlus