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 ( 1 H 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 2,5diketopiperazines against phytopathogenic microorganism enforcing their potential development as biopesticides.

Antimicrobial and Antibiofilm Activities of the Fungal Metabolites Isolated from the Marine Endophytes Epicoccum nigrum M13 and Alternaria alternata 13A

“…Li et al isolated two cyclic dipeptides, cyclo( d -Pro- l -Tyr), and cyclo( l -Pro- l -Tyr) from Lactobacillus reuteri and found that the latter exhibited antibacterial activity against Staphylococcus aureus [ 34 ]. Cimmino et al have isolated five DKPs, cyclo( l -Pro- l -Tyr), cyclo( l -Pro- l -Val), cyclo( d -Pro- d -Phe), cyclo( l -Pro- l -Leu), and cyclo( d -Pro- l -Tyr) with antibacterial activity against phytopathogenic Gram-positive bacterium Rhodococcus fascians LMG 3605 [ 35 ]. Cyclo( l -Pro- l -Phe), produced by Pseudonocardia endophytica , showed antibacterial activity against Gram-negative bacteria ( Xanthomonas campestris and Xanthomonas malvacearum ) and antifungal activity against ( Fusarium oxysporum and Fusarium solani ) [ 36 ].…”

Lysobacter penaei sp. nov., isolated from intestinal content of a Pacific white shrimp (Penaeus vannamei)

“…Strains of the genus Lysobacter are Gram-stain-negative, non-flagellated and flexing thin rods forming mucoid colonies [1]. Researchers are very interested in Lysobacter strains for their potential of producing mycolytic and bacteriolytic enzymes and antibiotic compounds [2–5]. Christensen and Cook first established the genus Lysobacter in 1978 [6] and, at the time of writing, this genus currently comprises 61 validly published and 12 invalidly published species (LSPN; www.bacterio.net) .…”

Characterisation of the Antibiotic Profile of Lysobacter capsici AZ78, an Effective Biological Control Agent of Plant Pathogenic Microorganisms

“…The latest studies on AZ78 metabolic profile strongly indicated that it is abundant in various antibiotic compound classes. Several bioactive 2,5-diketopiperazines have been identified and/or isolated from extracts of AZ78 cultures grown on nutrient-rich growth media [ 19 , 23 ]. Furthermore, genetic and analytical results have indicated the production of other bioactive compounds by AZ78 probably related to HSAF and WAP-8294A derivatives [ 24 ].…”

“…Extracts were evaluated for their antibacterial activity against Rhodococcus fascians LMG 3605 and anti-oomycete activity against P. ultimum using a resazurin-based microtitre assay. Antibacterial assays against R. fascians were performed as previously described by [ 23 ]. In brief, 140 µL of LB 1:10 were added to the wells of a sterile 96-well microtitre plate and amended with 20 µL of extract.…”

“…Indeed, AZ78 showed in vitro inhibitory activity against several important plant pathogenic fungi and oomycetes (e.g., Botrytis cinerea , Pythium ultimum ) and several Gram-positive plant pathogenic bacteria (e.g., Rhodococcus fascians) [ 20 ]. When grown in nutrient-rich conditions, AZ78 produced an array of 2,5-diketopiperazines (e.g., cyclo(L-Pro-L-Tyr)), some of which showed inhibitory activity against plant pathogenic microorganisms [ 19 , 23 ]. Recently, the Matrix-Assisted Laser Desorption/Ionisation-Orthogonal Time of Flight Mass Spectrometric Imaging (MALDI-qTOF-MSI) technique allowed the detection of signals pointing to the release of the antimicrobial HSAF, maltophilin and WAP-8294A2 by AZ78 [ 24 ].…”