Synthesis of Cis-2-Unsaturated fatty acids for biochemical control of biofilm production in Xylella fastidiosa

Different chemical species are utilized from bacteria as signals for cell-to-cell communication during Quorum Sensing. A widely investigated family of chemical signals from plant pathogenic bacteria are the diffusible signal factors (DSFs). In Xylella fastidiosa and related Xanthomonas species, these DSFs are produced by a synthase (RpfF) and interact with a cognate sensor (RpfC), resulting in the activation of a response regulator (RpfG) able of coordinating genes involved in the expression of virulence, spreading and biofilm formation. By recent investigations, X. fastidiosa exploits cis-2-unsaturated fatty acids as its own DSFs, and an imbalance in their concentration in bacterial cells seem to provoke blockage of xylem infection, by altering biofilm formation and architecture in a strategy called “pathogen confusion”. Here we report the synthesis of cis-2-unsaturated fatty acids with a chemical structure related to DSFs family, in order to test the in vitro alteration of biofilm production in X. fastidiosa ‘De Donno’ strain, the etiological agent of Olive Quick Decline Syndrome in Apulia region. A modified olefination stereoselective reaction of Horner-Emmons, called Still-Gennari, allowed for the synthesis of alfa-beta unsaturated fatty acids in cis (Z) conformation starting from commercial aldehydes. A preliminary investigation is carried out testing different commercial cis-2- unsaturated fatty acids (cis-2-decenoic acid, cis-2-dodecenoic acid, cis-2-(11)-methyldodecenoic acid) known as DSFs in Xanthomonas, Burkholderia and Pseudomonas genera, for their effect on X. fastidiosa ability to form a biofilm ring adhering to the surface of glass tubes or microtiter plates. These in vitro assays will be used to test the synthesized alfa-beta unsaturated fatty acids