Disalicylic Acid Provides Effective Control of Pectobacterium brasiliense

Bis(2-carboxyphenyl) succinate (disalicylic acid; DSA) is composed of two salicylic acids connected by a succinyl linker. Here, we propose its use as a new, synthetic plant-protection agent. DSA was shown to control Pectobacterium brasiliense, an emerging soft-rot pathogen of potato and ornamental crops, at minimal inhibitory concentrations (MIC) lower than those of salicylic acid. Our computational-docking analysis predicted that DSA would inhibit the quorum-sensing (QS) synthase of P. brasiliense ExpI more strongly than SA would. In fact, applying DSA to P. brasiliense inhibited its biofilm formation, secretion of plant cell wall-degrading enzymes, motility and production of acyl-homoserine lactones (AHL) and, subsequently, impaired its virulence. DSA also inhibited the production of AHL by a QS-negative Escherichia coli strain (DH5 alpha) that had been transformed with P. brasiliense AHL synthase, as demonstrated by the biosensors Chromobacterium violaceaum CV026 and E. coli pSB401. Inhibition of the QS machinery appears to be one of the mechanisms by which DSA inhibits specific virulence determinants. A new route is proposed for the synthesis of DSA, which holds greater potential for use as an anti-virulence agent than its precursor SA. Based on these findings, DSA is an excellent candidate for repurposing for new applications.

Automated summary

Bis(2-carboxyphenyl) succinate (disalicylic acid; DSA) was found to be a more effective synthetic plant-protection agent than salicylic acid, inhibiting the growth and virulence of Pectobacterium brasiliense. It was predicted to inhibit the quorum-sensing synthase of P. brasiliense more strongly than salicylic acid. DSA inhibited the biofilm formation, secretion of plant cell wall-degrading enzymes, motility, and production of acyl-homoserine lactones of P. brasiliense, as well as AHL production in a QS-negative Escherichia coli strain.