Physiochemically distinct SU-8 surfaces tailor Xylella fastidiosa cell-surface holdfast and colonization

SU-8 polymer is an excellent platform for diverse applications due to its high aspect ratio of micro/nanostructures fabrication and exceptional optical, chemical, and biocompatible properties. Although SU-8 has been often investigated for a variety of biological applications, how its surface properties influence both the interaction of bacterial cells with the substrate and its colonization is poorly understood. In this work, we tailor SU-8 nanoscale surface properties to investigate single cell motility, adhesion and successive colonization of a phytopathogenic bacteria, Xylella fastidiosa. Different surface properties of SU-8 thin films have been prepared using photolithography processing and oxygen plasma treatment. We found a significant difference in bacterial cell behavior and subsequent colonization on SU-8 as surface property changes. A larger density of carboxyl groups in hydrophilic plasma-treated SU-8 surfaces promotes faster cell motility in the earlier stage of the growth. The hydrophobic nature of pristine SU-8 surfaces has no trackable bacterial motility with 5 to 10 times more single cells adhered to surface than its plasma-treated counterpart. In fact, plasma-treated SU-8 samples suppressed bacterial adhesion, with surfaces showing less than 5% coverage. These results not only showcase that SU-8 surface properties can impact the bacterial behavior in a spatiotemporal manner, but also provide insights on the prominent ability of pathogens to evolve and adapt to different surface properties.