Homospermidine Lipids: A Compound Class Specifically Formed during Fruiting Body Formation of Myxococcus xanthus DK1622

Abstract

The fascinating ability of myxobacteria to form multicellular spore filled fruiting bodies under starvation conditions was widely studied as a model for cooperative microbial behavior. The potential of a life cycle induced change of secondary metabolism, as a means to discover novel natural products, remains largely underexplored. We therefore studied the model organism Myxococcus xanthus DK1622 under submersed and solid cultivation conditions to find putatively life-cycle related compounds by applying statistical analysis on analytical data. Utilizing the advantageous characteristics of LC-MS, LC-MS/MS, and MALDI-MSI allowed the identification of compounds unambiguously associated with myxobacterial fruiting bodies. Our screening effort resulted in the purification and structure elucidation of a novel compound, the homospermidine lipid, from cultures that had undergone the fruiting process. A combination of molecular networking and targeted LC-MS/MS in conjunction with our in-house metabolomics database subsequently revealed alternative producers of the respective compound as well as a number of compounds belonging to the same structural class. Three further members of this compound class were isolated from an alternative producer and structurally elucidated by NMR. Insights into the biosynthesis of this novel compound class was gained by feeding of isotopically labeled substrates and in silico analysis.

Spatiochemically Profiling Microbial Interactions with Membrane Scaffolded Desorption Electrospray Ionization-Ion Mobility-Imaging Mass Spectrometry and Unsupervised Segmentation

“…Historically, the discovery of secondary metabolites has been conducted via bioassay guided isolation from microbial liquid monocultures. − However, recent innovations in natural product discovery have demonstrated novel secondary metabolite production from microbes in solid-phase growth . Indeed, microbial competition and other mixed culture phenomena induce broad changes in the measurable metabolome in comparison to individual monocultures. − Typically, metabolomic changes are measured via reversed phase liquid chromatography–electrospray ionization-mass spectrometry (RPLC–ESI-MS). ,, However, in these experiments, there is a loss of the spatial expression patterns of metabolites, which may reveal functional roles.…”

“…Imaging mass spectrometry (IMS) is conducive to sampling microbes under planar solid-phase growth conditions. This technique can be used to assess chemical-spatial phenotypes by correlating the location of measured metabolites to observed microbial morphologies . These spatial correlations provide a significant advantage in assessing the functional roles of natural products.…”

Synergizing the potential of bacterial genomics and metabolomics to find novel antibiotics

“…It allows, for example, pinpointing secondary metabolites linked to bacterial life cycle stages such as sporulation as it was shown for the myxobacterium Myxococcus xanthus . 43 Co-cultivation experiments followed up by MALDI-MSI with termite gut-associated Streptomyces strains and a Pleosporales fungus showed spatially resolved appearance of a novel lanthipeptide that only appears in the co-cultivation contact zone. 44 These secondary metabolites appearing in the contact zone of a co-cultivation experiment are of particular interest as these molecules are often secreted as defence secondary metabolites that are predestined to become initial lead structures in antibiotics development.…”

Myxobakterielle Naturstofffabriken

“…Je nach Wahl des analytischen Ansatzes lassen sich weitere Substanzen entdecken. So charakterisierten wir erst kürzlich durch Vergleich von HPLC-MS-und MALDI-Imaging-Messungen Homospermidinlipid als neuen Sekundärmetaboliten, den DK1622 spezifisch während der Fruchtkörperentstehung bildet [8]. Alkylpyron (Abb.…”