Unraveling the Secrets of Bacterial Adhesion Organelles Using Single-Molecule Force Spectroscopy

Axner, Ove; Björnham, Oscar; Castelain, M.; Koutris, Efstratios; Schedin, Staffan; Fällman, Erik; Andersson, Magnus

doi:10.1007/978-3-642-02597-6_18

Cited by 15 publications

(18 citation statements)

References 50 publications

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“…2A1 and B1 for individual CS2 and CFA/I fimbriae, respectively. The responses comprised three distinct force regions, which are typical for helical fimbriae, including an increasing force, a constant force, and an increasing force (29). As found from previous studies, the CS2 and CFA/I fimbriae unwound at a constant force of 10 pN and 7.5 pN, respectively (8,12).…”

Section: Resultssupporting

confidence: 62%

Antibodies Damage the Resilience of Fimbriae, Causing Them To Be Stiff and Tangled

et al. 2017

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As adhesion fimbriae are a major virulence factor for many pathogenic Gram-negative bacteria, they are also potential targets for antibodies. Fimbriae are commonly required for initiating the colonization that leads to disease, and their success as adhesion organelles lies in their ability to both initiate and sustain bacterial attachment to epithelial cells. The ability of fimbriae to unwind and rewind their helical filaments presumably reduces their detachment from tissue surfaces with the shear forces that accompany significant fluid flow. Therefore, the disruption of functional fimbriae by inhibiting this resilience should have high potential for use as a vaccine to prevent disease. In this study, we show that two characteristic biomechanical features of fimbrial resilience, namely, the extension force and the extension length, are significantly altered by the binding of antibodies to fimbriae. The fimbriae that were studied are normally expressed on enterotoxigenic Escherichia coli, which are a major cause of diarrheal disease. This alteration in biomechanical properties was observed with bivalent polyclonal antifimbrial antibodies that recognize major pilin subunits but not with the Fab fragments of these antibodies. Thus, we propose that the mechanism by which bound antibodies disrupt the uncoiling of natural fimbria under force is by clamping together layers of the helical filament, thereby increasing their stiffness and reducing their resilience during fluid flow. In addition, we propose that antibodies tangle fimbriae via bivalent binding, i.e., by binding to two individual fimbriae and linking them together. Use of antibodies to disrupt physical properties of fimbriae may be generally applicable to the large number of Gram-negative bacteria that rely on these surface-adhesion molecules as an essential virulence factor. IMPORTANCE Our study shows that the resiliency of colonization factor antigen I (CFA/I) and coli surface antigen 2 (CS2) fimbriae, which are current targets for vaccine development, can be compromised significantly in the presence of antifimbrial antibodies. It is unclear how the humoral immune system specifically interrupts infection after the attachment of enterotoxigenic Escherichia coli (ETEC) to the epithelial surface. Our study indicates that immunoglobulins, in addition to their welldocumented role in adaptive immunity, can mechanically damage the resilience of fimbriae of surface-attached ETEC, thereby revealing a new mode of action. Our data suggest a mechanism whereby antibodies coat adherent and free-floating bacteria to impede fimbrial resilience. Further elucidation of this possible mechanism is likely to inform the development and refinement of preventive vaccines against ETEC diarrhea.KEYWORDS pili, IgG, vaccine, CFA/I, CS2, optical tweezers

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Section: Resultssupporting

confidence: 62%

Antibodies Damage the Resilience of Fimbriae, Causing Them To Be Stiff and Tangled

et al. 2017

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“…The fact that the main part of the pili expressed by UPEC bacteria constitutes a rod that is assembled from a number of subunits arranged in a helix-like quaternary structure provides the pili with a unique and rather intricate force-vs.-elongation behavior. Extensive descriptions of the basic features giving rise to this behavior have been given previously in the literature (Andersson et al 2006c;Axner et al 2009). To facilitate the interpretation of the data taken and to provide a useful nomenclature for the analysis, a brief summary is given here.…”

Section: Theorymentioning

confidence: 99%

“…Andersson et al 2006a;Axner et al 2009), referred to as dynamic conditions, the refolding rate in Eq. (1) can be neglected and the uncoiling force, denoted by D UC F , depends on the elongation speed in a logarithmic manner, i.e.…”

mentioning

confidence: 99%

Fast uncoiling kinetics of F1C pili expressed by uropathogenic Escherichia coli are revealed on a single pilus level using force-measuring optical tweezers

et al. 2010

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Uropathogenic Escherichia coli (UPEC) express various kinds of organelles, so-called pili or fimbriae, that mediate adhesion to host tissue in the urinary tract through specific receptor-adhesin interactions. The biomechanical properties of these pili have been considered important for the ability of bacteria to withstand shear forces from rinsing urine flows. Force-measuring optical tweezers have been used to characterize individual organelles of F1C type expressed by UPEC bacteria with respect to such properties. Qualitatively, the force-versus-elongation response was found to be similar to that of other types of helix-like pili expressed by UPEC, i.e., type 1, P, and S, with force-induced elongation in three regions, one of which represents the important uncoiling mechanism of the helix-like quaternary structure. Quantitatively, the steady-state uncoiling force was assessed as 26.4 ±1.4 pN, which is similar to those of other pili (which range from 21 pN for S(I) to 30 pN for type 1). The corner velocity for dynamic response (1,400 nm/s) was found to be larger than those of the other pili (400-700 nm/s for S and P pili, and 6 nm/s for type 1). The kinetics were found to be faster, with a thermal opening rate of 17 Hz, a few times higher than S and P pili, and three orders of magnitude higher than type 1. These data suggest that F1C pili are, like P and S pili, evolutionarily selected to primarily withstand the conditions expressed in the upper urinary tract.

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“…Mechanical response of the CS2 fimbriae to force was measured using optical-tweezers force spectroscopy under steady-state conditions (38). According to our homology modeling data, CotA showed a negative charge distribution on the outer surface, suggesting the possibility of a strong nonspecific interaction with positively charged amidine microspheres.…”

Section: Cs2 Fimbrial Response To Tensile Forcementioning

confidence: 99%

Biomechanical and Structural Features of CS2 Fimbriae of Enterotoxigenic Escherichia coli

Mortezaei

Singh

Zakrisson

et al. 2015

Biophysical Journal

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Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrhea worldwide, and infection of children in under-developed countries often leads to high mortality rates. Isolated ETEC expresses a plethora of colonization factors (fimbriae/pili), of which CFA/I and CFA/II, which are assembled via the alternate chaperone pathway (ACP), are among the most common. Fimbriae are filamentous structures whose shafts are primarily composed of helically arranged single pilin-protein subunits, with a unique biomechanical ability to unwind and rewind. A sustained ETEC infection, under adverse conditions of dynamic shear forces, is primarily attributed to this biomechanical feature of ETEC fimbriae. Recent understanding about the role of fimbriae as virulence factors points to an evolutionary adaptation of their structural and biomechanical features. In this work, we investigated the biophysical properties of CS2 fimbriae from the CFA/II group. Homology modeling of its major structural subunit, CotA, reveals structural clues related to the niche in which they are expressed. Using optical-tweezers force spectroscopy, we found that CS2 fimbriae unwind at a constant force of 10 pN and have a corner velocity (i.e., the velocity at which the force required for unwinding rises exponentially with increased speed) of 1300 nm/s. The biophysical properties of CS2 fimbriae assessed in this work classify them into a low-force unwinding group of fimbriae together with the CFA/I and CS20 fimbriae expressed by ETEC strains. The three fimbriae are expressed by ETEC, colonize in similar gut environments, and exhibit similar biophysical features, but differ in their biogenesis. Our observation suggests that the environment has a strong impact on the biophysical characteristics of fimbriae expressed by ETEC.

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Unraveling the Secrets of Bacterial Adhesion Organelles Using Single-Molecule Force Spectroscopy

Cited by 15 publications

References 50 publications

Antibodies Damage the Resilience of Fimbriae, Causing Them To Be Stiff and Tangled

Antibodies Damage the Resilience of Fimbriae, Causing Them To Be Stiff and Tangled

Fast uncoiling kinetics of F1C pili expressed by uropathogenic Escherichia coli are revealed on a single pilus level using force-measuring optical tweezers

Biomechanical and Structural Features of CS2 Fimbriae of Enterotoxigenic Escherichia coli

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