Isolation of 2,5-diketopiperazines from Lysobacter capsici AZ78 with activity against Rhodococcus fascians

Abstract

Inhibitory activity of the biocontrol bacterial strain Lysobacter capsici AZ78 is related to the production of cyclo(l-Pro-l-Tyr), a 2,5-diketopiperazine with in vitro and in vivo toxic activity against Phytophthora infestans and Plasmopara viticola. Further investigation of culture filtrate organic extracts showed its ability to produce other 2,5-diketopiperazines. They were isolated and identified by spectroscopic (¹H NMR and ESIMS) and physic (specific optical rotation) methods as cyclo(l-Pro-l-Val), cyclo(d-Pro-d-Phe), cyclo(l-Pro-l-Leu), and cyclo(d-Pro-l-Tyr). When tested against the phytopathogenic Gram-positive bacterium Rhodococcus fascians LMG 3605, cyclo(l-Pro-l-Val) showed a toxic activity similar to chloramphenicol at a comparable concentration. Overall, these data suggest that 2,5-diketopiperazines represent a class of metabolites characterizing the metabolome of L. capsici AZ78. Furthermore, the toxic activity showed by cyclo(l-Pro-l-Val) against R. fascians LMG 3605 broaden the spectrum activity of 2,5-diketopiperazines against phytopathogenic microorganisms enforcing their potential development as biopesticides.

Keywords:

• Lysobacter capsici
• cyclic dipeptides
• 25-diketopiperazines
• biopesticides
• Rhodococcus fascians

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was funded by Programme STAR 2017, financially supported by UniNA and Compagnia di San Paolo, grant number E62F16001250003. A. Evidente is associated with “Istituto di Chimica Biomolecolare del CNR”, Pozzuoli.