Role of Flagella in Adhesion of Escherichia coli to Abiotic Surfaces

Abstract

The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters. Abstract: Understanding the interfacial activity of bacteria is of critical importance due to the huge economic and public health implications associated with surface fouling and biofilm formation. The complexity of the process and difficulties of predicting microbial adhesion to novel materials demand study of the properties of specific bacterial surface features and their potential contribution to surface attachment. Here, we examine flagella, cell appendages primarily studied for their cell motility function, to elucidate their role in surface adhesion of Escherichia coli-a model organism and potential pathogen. We use self-assembled monolayers (SAMs) of thiol-bearing molecules on gold films to generate surfaces of varying hydrophobicity, and measure adhesion of purified flagella using quartz crystal microbalance. We show that flagella adhere more extensively and bind more tightly to hydrophobic SAMs than to hydrophilic ones, and propose a two-step vs a single-step adhesion mechanism that accounts for the observed dissipation and frequency changes for the two types of surfaces, respectively. Subsequently, study of the adhesion of wild-type and flagella knock-out cells confirms that flagella improve adhesion to hydrophobic substrates, whereas cells lacking flagella do not show preferred affinity to hydrophobic substrates. Together, these properties bring about an interesting ability of cells with flagella to stabilize emulsions of aqueous culture and dodecane, not observed for cells lacking flagella. This work contributes to our overall understanding of nonspecific bacterial adhesion and suggests that flagella, beyond motility, may play an important role in surface adhesion.Introduction:

Plasticity of Candida albicans Biofilms

“…This transition can be associated with a change in cellular phenotype. For instance, when motile bacteria, such as Escherichia coli, adhere to a substratum (33,82,83), motility ceases, cell multiplication continues (84)(85)(86)(87), and early biofilm-related genes are upregulated, including those that encode additional adhesins (88)(89)(90). Although Karatan and Watnick (91) suggested that bacteria at this point can form either an adherent monolayer biofilm or a multilayer biofilm, the former is not sufficient to encompass some of the main characteristics of a complex biofilm, most notably the formation of ECM and a three-dimensional, controlled microenvironment that facilitates biofilm growth, nutrient acquisition, control of gas and pH, and cell-cell signaling (92)(93)(94)(95)(96)(97).…”

Bacterial Interactions with Immobilized Liquid Layers

“…[13] For flagellated species such as E. coli and P. aeruginosa, flagella can play an additional role in both reversible and irreversible attachment on solid surfaces. [14][15][16] In nearly all cases, however, bacteria that interact with a solid will either irreversibly attach to a surface and begin producing extracellular polymeric substances (EPS) to eventually form a biofilm, or they will leave the surface and return to the planktonic state. [17] The shear stress created by flow conditions has been shown to enhance bacterial cell attachment to surfaces for a number of different species in a variety of ways, including the activation of catch-bonds in E. coli [18] and increasing the surface residence time of P. aeruginosa.…”

Bacterial flagella disrupt host cell membranes and interact with cytoskeletal components

“…It has been demonstrated that E. coli H48 flagella are generally attracted to hydrophobic surfaces and are ten times more likely than the bacterial cell body to make contact with artificial surfaces. These collisions by flagella with hydrophobic abiotic surfaces are known to slow bacteria down, promoting adhesion (39,40). This is also true in near surface swimming, a biophysical process dependent on rotating flagella, which has been shown to aid cooperative colonisation by probing and facilitating docking at membrane protrusions (41,42).…”