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. 2006 Mar 15;90(6):2206-12.
doi: 10.1529/biophysj.105.064592. Epub 2005 Dec 16.

Fluctuation analysis of Caulobacter crescentus adhesion

Elnaz Alipour-Assiabi  1 , Guanglai Li, Thomas R Powers, Jay X Tang
Affiliations

Fluctuation analysis of Caulobacter crescentus adhesion

Elnaz Alipour-Assiabi et al. Biophys J. .

Abstract

The aquatic bacterium Caulobacter crescentus divides asymmetrically to a flagellated swarmer cell and a cell with a stalk. At the end of the stalk is an adhesive organelle known as the holdfast, which the stalked cell uses to attach to a solid surface. Often there are two or more cells with their stalks attached to the same holdfast. By analyzing the fluctuations in the stalk angle for a pair of cells attached to a single holdfast, we determine the elastic stiffness of the holdfast. We model the holdfast as three torsional springs in series and find that the effective torsional spring constant for the holdfast is of the order of (10(-17)-10(-18)) Nm, with unequal spring constants. The asymmetry suggests the sequence in which the cells attach to each other, and in some cases suggests that strong crosslinks form between the stalks as they make a shared holdfast.

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Figures

FIGURE 1
FIGURE 1
A sketch of our model. The θi-values are the deviations from the equilibrium position and the ki-values are the elastic constants of each torsional spring. The counterclockwise direction is positive for all angles.
FIGURE 2
FIGURE 2
A primitive rosette formed by attachment of two stalked cells. The cell on the right is a predivisional cell, indicated by a constriction one-third of the way from the top.
FIGURE 3
FIGURE 3
(A) Raw data of angular fluctuations and (B) angular correlation as a function of time for the stalk angle of a single, isolated cell. The solid line is the single exponential fit on the experimental data. Only the points before (t = 40 ms) have been used for the fit, since the data become noisy after 40 ms (data not shown).
FIGURE 4
FIGURE 4
A histogram for ki-values for all the samples studied.
FIGURE 5
FIGURE 5
Experimental correlation data for sample 4. The curves are fits to the data using our theoretical correlation functions and k1, k2, k3, r1, and r2 as fitting parameters.
FIGURE 6
FIGURE 6
Experimental correlation data for sample 8. The curves are fits to the data using our theoretical correlation functions and k1, k2, k3, r1, and r2 as fitting parameters.
FIGURE 7
FIGURE 7
Theoretical cross-correlation function versus time for various k3, for a/R = 0.1 and k1 = k2.
FIGURE 8
FIGURE 8
Theoretical cross-correlation function versus time for a/R = 0.0 and for a/R = 0.1 and k1 ≪ k2 = k3, demonstrating that the hydrodynamic interaction is small.
FIGURE 9
FIGURE 9
Theoretical cross-correlation function versus time for a/R = 0.1, k2 = k3 and varying k1. (Dotted line, k1 = 0; dashed line, k1 = 0.5 k2; solid line, k1 = k2; and the dashed-dot line, k1 = 5 k2.)
FIGURE 10
FIGURE 10
Schematic drawings of two possible cell attachments: (I) stronger elastic coupling between the stalks; (II) weaker elastic coupling between them.
See this image and copyright information in PMC

References

    1. Poindexter, J. S. 1964. Biological properties and classification of the Caulobacter crescentus group. Bacteriol. Rev. 28:231–295. - PMC - PubMed
    1. Poindexter, J. S., and G. Cohen-Bazire. 1964. The fine structure of stalked bacteria belonging to the family Caulobacteraceae. J. Cell Biol. 23:587–607. - PMC - PubMed
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