posted on 2021-02-17, 17:55authored byTien Duy Vo, Christoph Spahn, Mike Heilemann, Helge B. Bode
Bacteria
produce a plethora of specialized metabolites (SM), with
the ecological function of most of them not known. A major group of
SM are peptides derived from nonribosomal peptide synthetases (NRPS).
In entomopathogenic bacteria of the genus Xenorhabdus, PAX (peptide-antimicrobial-Xenorhabdus) were described
as NRPS-derived lipopeptides, which show antimicrobial activities
against bacteria and fungi. We analyzed the production of PAX in Xenorhabdus doucetiae and found the majority bound to the
cells. We derivatized PAX with fluorophores and show binding to cells
when added externally using super-resolution microscopy. Externally
added PAX in X. doucetiae and E. coli as well as inducible PAX production in X. doucetiae showed a protective effect against various antimicrobial peptides
(AMPs) from insects, where they are used as a defense mechanism against
pathogens. Because AMPs are often positively charged, our results
suggest a PAX-induced repulsive force due to positive charge at the
bacterial cell wall.