Isolation and activity ofXenorhabdusantimicrobial compounds against the plant pathogensErwinia amylovoraandPhytophthora nicotianae

Abstract

Aims: 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. Methods and 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® 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. Significance and Impact of the Study: 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.

A Xenorhabdus budapestensis entomopatogén baktérium sejtmentes fermentlevének és tisztítottfehérje-frakciójának antimikrobiális hatása néhány zoonoticus baktériumra

“…A Xenorhabdus budapestensis rovarpatogén nematodák bélcsövében élő Gram-negatív baktérium, amelynek anyagcseretermékei között antimikrobiális aktivitású peptidek találhatóak [1], s bicornutin-A néven került leírásra. 2014-ben publikálták [2], hogy ez a fehérje nemcsak egy hexapeptidből áll, hanem egy egész hibridmolekulafehérje-család, amely a fabclavin elnevezést kapta.…”

“…Az antimikrobiális hatással rendelkező fehérje egyaránt hatékony volt előzetes kísérleteinkben növényi patogénen (Erwinia amylovora [1]), valamint állat-egész-ségügyi szempontból jelentős a tehenek mastitisét kiváltó baktériumokon (Staphylococcus aureus, Klebsiella pneumoniae) in vitro kísérletekben [3,4]. E tesztelésre kiválasztott baktériumtörzsek azért szá-mítanak különlegesnek, mert nagy részüket nem tesztelték az említett peptiddel szemben.…”

Trophic Relationships of Entomopathogenic Nematodes in Agricultural Habitats

“…tabaci, Pseudomonadales: Pseudomonadaceae) and Ralstonia solanacearum (Smith) (Burkholderiales: Ralstoniaceae). Three bicornutins, (A, B and C), have also been detected (Böszörményi et al, 2009;Fodor et al, 2012;Hinchliffe et. al., 2010).…”

Overview of the Basic Biology of Bacillus thuringiensis with Emphasis on Genetic Engineering of Bacterial Larvicides for Mosquito Control

“…are secreted and protect the cadaver from contaminating organisms during its bioconversion. Xenorhabdus has been reported to produce a whole range of antimicrobials based on secondary metabolites and linear and cyclic peptides, such as benzylideneacetone, nematophin, xenocoumacins 1 and 2, xenortides A and B, xenematide, and the bicornutins A, B and C [62][63][64][65][66][67]. P. luminescens strains have been reported to produce the antimicrobials 2-isopropyl-5-(3-phenyl-oxiranyl)-benzene-1,3-diol, 3,5,-dihydroxy-4-isopropyl-stilbene and the -lactam carbapenem as well as a whole host of small organic compounds synthesised by large polyketide synthetase genes [67][68][69][70][71].…”