Isolation and activity of Xenorhabdus antimicrobial compounds against the plant pathogens Erwinia amylovora and Phytophthora nicotianae.
OBJECTIVE
Broad-spectrum antibiotics produced by symbiotic bacteria [entomopathogenic bacterium (EPB)] of entomopathogenic nematodes keep monoxenic conditions in insect cadavers in soil. This study evaluated antibiotics produced by EPB for their potential to control plant pathogenic bacteria and oomycetes.


RESULTS
Entomopathogenic bacterium produce antibiotics effective against the fire blight bacterium Erwinia amylovora, including streptomycin resistant strains, and were as effective in phytotron experiments as kasugamycin or streptomycin. Xenorhabdus budapestensis and X. szentirmaii antibiotics inhibited colony formation and mycelial growth of Phytophthora nicotianae. From X. budapestensis, an arginine-rich fraction (bicornutin) was adsorbed by Amberlite((R)) XAD 1180, and eluted with methanol : 1 n HCI (99 : 1). Bicornutin inactivated zoospores, and inhibited germination and colony formation of cystospores at <<25 ppm. An UV-active molecule (bicornutin-A, MW = 826), separated by HPLC and thin-layer chromatography, was identified as a novel hexa-peptide : RLRRRX.


CONCLUSIONS
Xenorhabdus budapestensis produces metabolites with strong antibacterial and cytotoxic activity. Individual compounds can be isolated, identified and patented, but their full antimicrobial potential may be multiplied by synergic interactions.


CONCLUSIONS
Active compounds of two new Xenorhabdus species might control plant diseases caused by pathogens of great importance to agriculture such as Erw. amylovora and P. nicotianae.
Böszörményi
E
E
Department of Genetics, Eötvös University, Budapest, Hungary.
Ersek
T
T
Fodor
A
A
Fodor
A M
AM
Földes
L Sz
LS
Hevesi
M
M
Hogan
J S
JS
Katona
Z
Z
Klein
M G
MG
Kormány
A
A
Pekár
S
S
Szentirmai
A
A
Sztaricskai
F
F
Taylor
R A J
RA