The role of conditioning film formation and surface chemical changes on Xylella fastidiosa adhesion and biofilm evolution

Abstract

Biofilms are complex microbial communities with important biological functions including enhanced resistance against external factors like antimicrobial agents. The formation of a biofilm is known to be strongly dependent on substrate properties including hydrophobicity/hydrophilicity, structure, and roughness. The adsorption of (macro)molecules on the substrate, also known as conditioning film, changes the physicochemical properties of the surface and affects the bacterial adhesion. In this study, we investigate the physicochemical changes caused by Periwinkle wilt (PW) culture medium conditioning film formation on different surfaces (glass and silicon) and their effect on X. fastidiosa biofilm formation. Contact angle measurements have shown that the film formation decreases the surface hydrophilicity degree of both glass and silicon after few hours. Atomic force microscopy (AFM) images show the glass surface roughness is drastically reduced with conditioning film formation. First-layer X. fastidiosa biofilm on glass was observed in the AFM liquid cell after a period of time similar to that determined for the hydrophilicity changes. In addition, attenuation total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy supports the AFM observation, since the PW absorption spectra increases with time showing a stronger contribution from the phosphate groups. Although hydrophobic and rough surfaces are commonly considered to increase bacteria cell attachment, our results suggest that these properties are not as important as the surface functional groups resulting from PW conditioning film formation for X. fastidiosa adhesion and biofilm development.

Biological responses of silver-coated thermosets: An in vitro and in vivo study

“…The latter include plasma proteins, mainly albumin, fibrinogen and fibronectin [33][34][35][36][37][38]. Moreover, the adsorbed ''conditioning'' film may influence the antimicrobial response by altering the physical-chemical properties of the surface and thus the aspecific bacterial adhesion mechanisms [39,40].…”

The physics of biofilms—an introduction

“…We now know that this is a very general process. These substances form a so-called "conditioning layer" that alters substantially the physicochemical properties of the substratum and its interaction with microorganisms [211,[254][255][256][257][258]. A surface may become selectively attractive to some cells.…”

Comparison of polycaprolactone and starch/polycaprolactone blends as carbon source for biological denitrification

“…Surface hydrophobicity of carriers was also an influencing factor for cell attachment. Usually, bacterial cells are hydrophilic, and the number of attached cells increased with the increase in surface hydrophobicity of carriers (Lorite et al 2011;Teixeira and Oliveira 1999). However, starch is hydrophilic material, and the presence of PCL led to a significant improvement of the material hydrophobicity (Averous et al 2000), suggesting that the hydrophilic of SPCL10 and SPCL12 was better than that of PCL.…”