Xenorhabdus khoisanae SB10 produces Lys-rich PAX lipopeptides and a Xenocoumacin in its antimicrobial complex
Date
2019-06-13
Journal Title
Journal ISSN
Volume Title
Publisher
BMC (part of Springer Nature)
Abstract
Background: Xenorhabdus spp. live in close symbiosis with nematodes of the Steinernema genus. Steinernema
nematodes infect an insect larva and release their symbionts into the haemocoel of the insect. Once released into
the haemocoel, the bacteria produce bioactive compounds to create a semi-exclusive environment by inhibiting
the growth of bacteria, yeasts and molds. The antimicrobial compounds thus far identified are xenocoumacins,
xenortides, xenorhabdins, indole derivatives, xenoamicins, bicornutin and a number of antimicrobial peptides. The
latter may be linear peptides such as the bacteriocins xenocin and xenorhabdicin, rhabdopeptides and cabanillasin,
or cyclic, such as PAX lipopeptides, taxlllaids, xenobactin and szentiamide. Thus far, production of antimicrobial
compounds have been reported for Xenorhabdus nematophila, Xenorhabdus budapestensis, Xenorhabdus cabanillasii,
Xenorhabdus kozodoii, Xenorhabdus szentirmaii, Xenorhabdus doucetiae, Xenorhabdus mauleonii, Xenorhabdus indica
and Xenorhabdus bovienii. Here we describe, for the first time, PAX lipopeptides and xenocoumacin 2 produced by
Xenorhabdus khoisanae. These compounds were identified using ultraperformance liquid chromatography, linked to
high resolution electrospray ionisation mass spectrometry and tandem mass spectrometry.
Results: Cell-free supernatants of X. khoisanae SB10 were heat stable and active against Bacillus subtilis subsp.
subtilis, Escherichia coli and Candida albicans. Five lysine-rich lipopeptides from the PAX group were identified in
HPLC fractions, with PAX1’ and PAX7 present in the highest concentrations. Three novel PAX7 peptides with
putative enoyl modifications and two linear analogues of PAX1’ were also detected. A small antibiotic compound,
yellow in colour and λmax of 314 nm, was recovered from the HPLC fractions and identified as xenocoumacin 2. The
PAX lipopeptides and xenocoumacin 2 correlated with the genes and gene clusters in the genome of X. khoisanae
SB10.
Conclusion: With UPLC-MS and MSe analyses of compounds in the antimicrobial complex of X. khoisanae SB10, a
number of PAX peptides and a xenocoumacin were identified. The combination of pure PAX1’ peptide with
xenocoumacin 2 resulted in high antimicrobial activity. Many of the fractions did, however, contain labile compounds
and some fractions were difficult to resolve. It is thus possible that strain SB10 may produce more antimicrobial
compounds than reported here, as suggested by the APE Ec biosynthetic complex. Further research is required to
develop these broad-spectrum antimicrobial compounds into drugs that may be used in the fight against microbial
infections.
Description
CITATION: Dreyer, J., et al. 2019. Xenorhabdus khoisanae SB10 produces Lys-rich PAX lipopeptides and a Xenocoumacin in its antimicrobial complex. BMC Microbiology, 19:132, doi:10.1186/s12866-019-1503-x.
The original publication is available at https://bmcmicrobiol.biomedcentral.com
The original publication is available at https://bmcmicrobiol.biomedcentral.com
Keywords
Khoisan (African people), Xenorhabdus, Antimicrobials
Citation
Dreyer, J., et al. 2019. Xenorhabdus khoisanae SB10 produces Lys-rich PAX lipopeptides and a Xenocoumacin in its antimicrobial complex. BMC Microbiology, 19:132, doi:10.1186/s12866-019-1503-x