Electric Potential-Induced Adhesion and Filamentation of Xylella Fastidiosa

Xylella fastidiosa is a plant photogenic bacterium responsible for various plant diseases, significantly impacting economically important crops such as grapevines, olive trees, and citrus plants. The adhesion of X. fastidiosa to surfaces is a critical step in biofilm formation, which is essential for its pathogenicity and persistence [1,2]. This study aimed to investigate the effect of electric potential on the adhesion of X. fastidiosa to dielectric-coated gold electrodes. Previous studies have indicated that Xylella fastidiosa exhibits a stronger adhesion affinity to gold compared to other abiotic and biotic substrates [3,4], which may be due to metal electronic structure; in our samples, we are able to modulate the potential at the surface of interdigitated gold electrodes coated with a dielectric layer. We explored the adhesion behavior X. fastidiosa on these electrodes at different electric potential differences ranging from 0 to 500 mV. The thin gold layers forming the electrodes were deposited by e-beam evaporation on SiO2/Si substrates, and subsequently coated with another SiO2 layer. X.fastidiosa growth was carried out in PW broth media. After a 24-hour growth period, we conducted analyses to observe specific behaviors at each applied electric bias. At 0 mV, adhesion occurred with single cells and small bacterial clusters, with X. fastidiosa cells maintaining their typical length of approximately 3-4 µm; similar behavior was observed for larger bias. However, at 300 mV, a significant presence of single filamented cells, reaching up to 10 µm, was noted, with no biofilms present in the samples. As bias increases to 500 mV, single cells were the most present on the surface, but with a larger dispersion in cell sizes, between 3 and 10µm. In terms of coverage area on the electrodes, the maximum coverage was observed at 0 mV, with a steady decrease as the applied electric potential difference increased. These results suggest a relationship between electric potential and cellular filamentation in the adhesion of X. fastidiosa to surfaces. Further studies are on the way to further the understanding and establish a clearer relationship between these phenomena.<br/>Acknowledgements: This work was financially supported by the Brazilian funding agencies CNPq and Fapesp (grant number 2019/07616-3).<br/>References:<br/>[1] S. Albumani, et al., npj Biofilms and Microbiomes 7 (2021) 86<br/>[2] R. Janissen, et al., Scientific reports 5 (2015) 9856<br/>[3] G. Lorite, et al., PLoS One 8 (2013) e75247<br/>[4] G. Lorite, et al., Journal of colloid and interface science 359 (2011) 289-295