Flagella-surface interactions

Biofilms, surface-bound communities of microbes, are economically and medically important due to their pathogenic and obstructive properties.

Among the numerous strategies to prevent bacterial adhesion and subsequent biofilm formation, surface topography presents a highly nonspecific method that does not rely on small-molecule antibacterial compounds, which promote resistance. Understanding how bacteria interact with surfaces that have roughness on the micrometer and submicrometer length scales (i.e., comparable with the length scale of the bacteria themselves) is critical to the development of antiadhesive topographies. Such surfaces are also relevant for a deeper understanding of the native bacterial lifestyle, because most surfaces in nature are not atomically smooth. Geometric considerations suggest that surfaces with roughness on the bacterial length scale provide less available surface area and fewer attachment points for rigid bacterial bodies than smooth surfaces.

However, the simplistic view of bacteria as rigid rods or spheres ignores the presence of bacterial appendages, such as pili and flagella ). We are currently studying the role of flagella in adhesion of E. coli to surfaces.

Publications

Friedlander RS, Vlamakis H, Kim P, Khan M, Kolter R, Aizenberg J. Bacterial flagella explore microscale hummocks and hollows to increase adhesion. Proc. Nat. Acad. Sci. [Internet]. 2013;110 (14) :5624-5629. Publisher's VersionAbstract
Biofilms, surface-bound communities of microbes, are economically and medically important due to their pathogenic and obstructive properties. Among the numerous strategies to prevent bacterial adhesion and subsequent biofilm formation, surface topography was recently proposed as a highly nonspecific method that does not rely on small-molecule antibacterial compounds, which promote resistance. Here, we provide a detailed investigation of how the introduction of submicrometer crevices to a surface affects attachment of Escherichia coli. These crevices reduce substrate surface area available to the cell body but increase overall surface area. We have found that, during the first 2 h, adhesion to topographic surfaces is significantly reduced compared with flat controls, but this behavior abruptly reverses to significantly increased adhesion at longer exposures. We show that this reversal coincides with bacterially induced wetting transitions and that flagellar filaments aid in adhesion to these wetted topographic surfaces. We demonstrate that flagella are able to reach into crevices, access additional surface area, and produce a dense, fibrous network. Mutants lacking flagella show comparatively reduced adhesion. By varying substrate crevice sizes, we determine the conditions under which having flagella is most advantageous for adhesion. These findings strongly indicate that, in addition to their role in swimming motility, flagella are involved in attachment and can furthermore act as structural elements, enabling bacteria to overcome unfavorable surface topographies. This work contributes insights for the future design of antifouling surfaces and for improved understanding of bacterial behavior in native, structured environments.

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