Holdfast spreading and thickening during Caulobacter crescentus attachment to surfaces

Yves V Brun,Jay X Tang,Guanglai Li

doi:10.1186/1471-2180-13-139

Yves V Brun, Jay X Tang + Show 1 more

Open Access

https://doi.org/10.1186/1471-2180-13-139

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Abstract

BackgroundAdhesion to surfaces facilitates many crucial functions of microbes in their natural habitats. Thus understanding the mechanism of microbial adhesion is of broad interest to the microbiology research community.ResultsWe report a study by fluorescence imaging and atomic force microscopy on the growth in size and thickness of the holdfast of synchronized Caulobacter crescentus cells as they attach to a glass surface. We found that the holdfast undergoes a two-stage process of spreading and thickening during its morphogenesis. The holdfast first forms a thin plate on the surface. The diameter of the holdfast plate reaches its final average value of 360 nm by the cell age of ~ 30 min, while its thickness further increases until the age of ~ 60 min. Our AFM analysis indicates that the holdfast is typically thicker in the middle, with gradual falloff in thickness towards the outer edge.ConclusionsWe propose that the newly secreted holdfast substance is fluid-like. It has strong affinity to the surface and cures to form a plate-like holdfast capable of supporting strong and permanent adhesion.

Highlights

Adhesion to surfaces facilitates many crucial functions of microbes in their natural habitats
In order to gain insight about the material properties of bacterial adhesins, we study the morphogenesis of the adhesive holdfast of the Gram negative bacterium Caulobacter crescentus
Adhesives have a broad range of biomedical applications, from denture to surgical suture

Summary

Introduction

Adhesion to surfaces facilitates many crucial functions of microbes in their natural habitats. The swarmer cell swims by rotating its single polar flagellum [3,4,5,6]. This mechanism allows for dispersal of the progeny cells following each division, which reduces local competition for nutrients. Reversible adhesion occurs in swarmer cells where initial surface interactions are mediated by the flagellum and pili [12]. Contact of the flagellum and pili with a surface increases the load on the flagellum motor, halting flagellum rotation and triggering just-in-time deployment of holdfast from the flagellar pole. In cells that do not contact a surface, holdfast synthesis is regulated by the developmental program and occurs in the late swarmer stage [11,12]. There has not been much study with respect to possible differences between these two pathways, since the contact-triggered C. crescentus adhesion pathway has only been discovered recently [12]

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