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Issue 16, 2017
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Substrate effects on cell-envelope deformation during early-stage Staphylococcus aureus biofilm formation

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Abstract

Bacterial adhesion to a surface is the first step in biofilm formation, and adhesive forces between the surface and a bacterium are believed to give rise to planktonic-to-biofilm phenotypic changes. Here we use Focused-Ion-Beam (FIB) tomography with backscattered scanning electron microscopy (SEM) to image Staphyolococcus aureus (S. aureus) biofilms grown on Au-coated polystyrene (PS) and Au-coated PS modified by mixed thiols of triethylene glycol mono-11-mercaptoundecyl ether (EG3) and 1-dodecanethiol (CH3). The FIB-SEM technique enables a direct measurement of the contact area between individual bacteria and the substrate. The area of adhesion is effectively zero on the EG3 substrate. It is nonzero on all of the other substrates and increases with increasing hydrophobicity. The fact that the contact area is highest on the unmodified gold, however, indicates that other forces beyond hydrophobicity are significant. The magnitude of bacterial deformation suggests that the adhesive forces are on the order of a few nN, consistent with AFM force measurements reported in the literature. The resolution afforded by electron microscopy furthermore enables us to probe changes in the cell-envelope thickness, which decreases within and near the contact area relative to other parts of the same bacterium. This finding supports the idea that mechanosensing due to stress-induced membrane thinning plays a role in the planktonic-to-biofilm transition associated with bacterial adhesion.

Graphical abstract: Substrate effects on cell-envelope deformation during early-stage Staphylococcus aureus biofilm formation

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Publication details

The article was received on 17 Dec 2016, accepted on 21 Mar 2017 and first published on 21 Mar 2017


Article type: Paper
DOI: 10.1039/C6SM02815B
Citation: Soft Matter, 2017,13, 2967-2976
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    Substrate effects on cell-envelope deformation during early-stage Staphylococcus aureus biofilm formation

    J. Gu, A. Valdevit, T. Chou and M. Libera, Soft Matter, 2017, 13, 2967
    DOI: 10.1039/C6SM02815B

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