Surface physicochemical properties at the micro and nano length scales: role on bacterial adhesion and Xylella fastidiosa biofilm development.

Gabriela S Lorite,Boris Mizaikoff,Carolina M Rodrigues,Alessandra A De Souza,João H Clerici,Christine Kranz,Juarez P Tomaz,Mônica A Cotta,Richard Janissen,Zoya Leonenko

doi:10.1371/journal.pone.0075247

Gabriela S Lorite, Boris Mizaikoff + Show 8 more

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https://doi.org/10.1371/journal.pone.0075247

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Abstract

The phytopathogen Xylella fastidiosa grows as a biofilm causing vascular occlusion and consequently nutrient and water stress in different plant hosts by adhesion on xylem vessel surfaces composed of cellulose, hemicellulose, pectin and proteins. Understanding the factors which influence bacterial adhesion and biofilm development is a key issue in identifying mechanisms for preventing biofilm formation in infected plants. In this study, we show that X. fastidiosa biofilm development and architecture correlate well with physicochemical surface properties after interaction with the culture medium. Different biotic and abiotic substrates such as silicon (Si) and derivatized cellulose films were studied. Both biofilms and substrates were characterized at the micro- and nanoscale, which corresponds to the actual bacterial cell and membrane/ protein length scales, respectively. Our experimental results clearly indicate that the presence of surfaces with different chemical composition affect X. fastidiosa behavior from the point of view of gene expression and adhesion functionality. Bacterial adhesion is facilitated on more hydrophilic surfaces with higher surface potentials; XadA1 adhesin reveals different strengths of interaction on these surfaces. Nonetheless, despite different architectural biofilm geometries and rates of development, the colonization process occurs on all investigated surfaces. Our results univocally support the hypothesis that different adhesion mechanisms are active along the biofilm life cycle representing an adaptation mechanism for variations on the specific xylem vessel composition, which the bacterium encounters within the infected plant.

Highlights

Biofilms are complex microbial communities associated with surfaces with important biological functions including bacterial infection and enhanced resistance against antimicrobial agents [1]
Such measurements on cellulosic materials have been extensively studied in literature [37]; for cellulose acetate (CA) and ethyl cellulose (EC) surfaces values range in the -10 to -50mV [38,39], depending on various parameters such as pH, polymer swelling, fiber structure, etc
Screening of such inomogeneities can occur in solution; this issue will be further addressed in the subsequent sections

Summary

Introduction

Biofilms are complex microbial communities associated with surfaces with important biological functions including bacterial infection and enhanced resistance against antimicrobial agents [1]. The bacterial biofilm life cycle is known as a multi-stage process, which current models subdivide into five development stages [2]. During all these stages, biofilm development may be mediated by a number of factors including nutrient environment, pH, temperature and surface properties [2]. Surface properties may be altered by the adsorption of (macro) molecules from the liquid environment onto the substrate forming a conditioning film, which has been considered as the initial step of biofilm formation [3,4,5]. Advanced understanding the influence of surfaces properties on biofilm formation will lead to strategies for preventing microbial adhesion, and biofilm development

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