Controlled spatial organization of bacterial clusters reveals cell filamentation is vital for Xylella fastidiosa biofilm formation

Abstract

The morphological plasticity of bacteria to form filamentous cells commonly represents an adaptive strategy induced by stresses. In contrast, for diverse pathogens filamentous cells have been observed during biofilm formation, with function yet to be elucidated. To identify prior hypothesized quorum sensing as trigger of such cell morphogenesis, spatially controlled cell adhesion is pivotal. Here, we demonstrate highly-selective cell adhesion of the biofilm-forming phytopathogen Xylella fastidiosa to gold-patterned SiO2 substrates with well-defined geometries and dimensions. The consequent control of both cell density and distances between cell clusters using these patterns provided evidence of quorum sensing governing filamentous cell formation. While cell morphogenesis is induced by cell cluster density, filamentous cell growth is oriented towards neighboring cell clusters and distance-dependent; large interconnected cell clusters create the early biofilm structural framework. Together, our findings and investigative platform could facilitate therapeutic developments targeting biofilm formation mechanisms of X. fastidiosa and other pathogens.

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

“…An in-depth understanding of the physicochemical aspects of bacterial-substratum interface is important both fundamentally and clinically for preventing microbial adhesion and consequently, biofilm infections [20,[26][27][28][29]. Moreover, the development of in vitro models to unraveling the spatiotemporal relationship to bacterial adhesion, cell motility and subsequent colonization has remained a key topic in biomedical research [22,30].…”

“…In particular, the entire biofilm formation process, starting from single cell adhesion, has been investigated, turning X. fastidiosa into a reliable bacterial model [24,32]. This species is also interesting as it shares many genetic traits with other human bacteria [33,34] and has relatively slow duplication time (~6h) [30], which renders easier the observation of surface colonization. Moreover, X. fastidiosa relies on type-IV pili, which are about 2-to-6-μm long, for twitching motility; these pili are significantly impacted by surface chemistry [35,36].…”