Physiochemical Properties of <i>Caulobacter crescentus</i> Holdfast: A Localized Bacterial Adhesive
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Abstract
To
colonize surfaces, the bacterium <i>Caulobacter crescentus</i> employs a polar polysaccharide, the holdfast, located at the end
of a thin, long stalk protruding from the cell body. Unlike many other
bacteria which adhere through an extended extracellular polymeric
network, the holdfast footprint area is tens of thousands times smaller
than that of the total bacterium cross-sectional surface, making for
some very demanding adhesion requirements. At present, the mechanism
of holdfast adhesion remains poorly understood. We explore it here
along three lines of investigation: (a) the impact of environmental
conditions on holdfast binding affinity, (b) adhesion kinetics by
dynamic force spectroscopy, and (c) kinetic modeling of the attachment
process to interpret the observed time-dependence of the adhesion
force at short and long time scales. A picture emerged in which discrete
molecular units called adhesins are responsible for initial holdfast
adhesion, by acting in a cooperative manner