DisplayTitle

Xanthomonas campestris Diffusible Factor Is 3-Hydroxybenzoic Acid and Is Associated with Xanthomonadin Biosynthesis, Cell Viability, Antioxidant Activity, and Systemic Invasion

¹Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673; ²State Key Laboratory of Microbial Metabolism and National Center for Molecular Characterization of GMOs, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China; ³State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Guangxi University, Nanning 530004, China

Xanthomonas campestris pv. campestris produces a membrane-bound yellow pigment called xanthomonadin. A diffusible factor (DF) has been reported to regulate xanthomonadin biosynthesis. In this study, DF was purified from bacterial culture supernatants using a combination of solvent extraction, flash chromatography, and high-performance liquid chromatography. Mass spectrometry and nuclear magnetic resonance analyses resolved the DF chemical structure as 3-hydroxybenzoic acid (3-HBA), which was further confirmed by synthetic 3-HBA. Significantly, bioassay and in silico analysis suggest that DF production is widely conserved in a range of bacterial species. Analysis of DF derivatives established the hydroxyl group and its position as the key structural features for the role of DF in xanthomonadin biosynthesis. In addition, we showed that DF is also associated with bacterial survival, H₂O₂ resistance, and systemic invasion. Furthermore, evidence was also presented that DF and diffusible signaling factor have overlapping functions in modulation of bacterial survival, H₂O₂ resistance, and virulence. Utilization of different mechanisms to modulate similar virulence traits may provide X. campestris pv. campestris with plasticity in response to various environmental cues.