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153 Publications visible to you, out of a total of 153
Genome Mining Reveals Endopyrroles from a Nonribosomal Peptide Assembly Line Triggered in Fungal-Bacterial Symbiosis

Abstract (Expand)

The bacterial endosymbiont (Burkholderia rhizoxinica) of the rice seedling blight fungus (Rhizopus microsporus) harbors a large number of cryptic biosynthesis gene clusters. Genome mining and sequence … similarity networks based on an encoded nonribosomal peptide assembly line and the associated pyrrole- forming enzymes in the symbiont indicated that the encoded metabolites are unique among a large number of tentative pyrrole natural products in diverse and unrelated bacterial phyla. By performing comparative metabolic pro fi ling using a mutant generated with an improved pheS Burkholderia counterselection marker, we found that the symbionts ’ biosynthetic pathway is mainly activated under salt stress and exclusively in symbiosis with the fungal host. The cryptic metabolites were fully characterized as novel pyrrole-substituted depsipeptides (endopyrroles). A broader survey showed that endopyrrole production is a hallmark of geographically distant endofungal bacteria, which produce the peptides solely under symbiotic conditions.

Authors: Sarah Niehs, Benjamin Dose, Kirstin Scherlach, Sacha J. Pidot, Timothy P. Stinear, Christian Hertweck

Date Published: 8th Jul 2019

Publication Type: Not specified

Genomics-driven discovery of a linear lipopeptide promoting host colonization by endofungal bacteria

Abstract (Expand)

The rice seedling blight fungus Rhizopus microsporus weakens or kills plants by means of a potent toxin produced by endobacteria (Burkholderia rhizoxinica) that live within the fungal hyphae. The success … of the highly attuned microbial interaction is partly based on the bacteria ’ s ability to roam and re-colonize the fungal host. Yet, apart from the toxin, chemical mediators of the symbiosis have remained elusive. By genome mining and comparison we identi fi ed a cryptic NRPS gene cluster that is conserved among all sequenced Rhizopus endosymbionts. Metabolic pro fi ling and targeted gene inactivation led to the discov- ery of a novel linear lipopeptide, holrhizin A, which was fully characterized. Through in vitro and in vivo assays we found that holrhizin acts (A) as a biosurfactant to reduce surface tension, (B) in fl uences the for- mation of mature bio fi lms and thus cell motility behavior that ultimately supports the bacterial cells to (C) colonize and invade the fungal host, consequently supporting the re-establishment of the exceptional Burkholderia-Rhizopus symbiosis. We not only unveil structure and function of an linear lipopeptide from endofungal bacteria but also provide a functional link between the symbiont’ s orphan NRPS genes and a chemical mediator that promotes bacterial invasion into the fungal host.

Authors: Sarah Niehs, Kirstin Scherlach, Christian Hertweck

Date Published: 31st Aug 2018

Publication Type: Not specified

Genomics-Driven Discovery of a Symbiont-Specific Cyclopeptide from Bacteria Residing in the Rice Seedling Blight Fungus

Abstract (Expand)

The rice seedling blight fungus Rhizopus microsporus harbors endosymbiotic bacteria (Burkholderia rhizoxinica) that produce the virulence factor rhizoxin and control host development. Genome mining … indicated a massive inventory of cryptic non- ribosomal peptide synthetase (NRPS) genes, which have not yet been linked to any natural products. The discovery and full characterization of a novel cyclopeptide from endofungal bac- teria is reported. In silico analysis of an orphan, symbiont-spe- cific NRPS predicted the structure of a nonribosomal peptide, which was targeted by LC-MS/MS profiling of wild-type and engineered null mutants. NMR spectroscopy and chemical deri- vatization elucidated the structure of the bacterial cyclopep- tide. Phylogenetic analyses revealed the relationship of starter C domains for rare N-acetyl-capped peptides. Heptarhizin is produced under symbiotic conditions in geographically con- strained strains from the Pacific clade; this indicates a potential ecological role of the peptide.

Authors: Sarah Niehs, Benjamin Dose, Kirstin Scherlach, Martin Roth, Christian Hertweck

Date Published: 16th Aug 2018

Publication Type: Not specified

Genomics-Driven discovery of natural products from symbiotic Burkholderia species

Abstract

Not specified

Editor:

Date Published: 20th Nov 2020

Publication Type: Doctoral Thesis

Genomics-Driven Discovery of NO-Donating Diazeniumdiolate Siderophores in Diverse Plant-Associated Bacteria.

Abstract (Expand)

Siderophores are key players in bacteria-host interactions, with the main function to provide soluble iron for their producers. Gramibactin from rhizosphere bacteria expands siderophore function and … diversity as it delivers iron to the host plant and features an unusual diazeniumdiolate moiety for iron chelation. By mutational analysis of the grb gene cluster, we identified genes (grbD and grbE) necessary for diazeniumdiolate formation. Genome mining using a GrbD-based network revealed a broad range of orthologous gene clusters in mainly plant-associated Burkholderia/Paraburkholderia species. Two new types of diazeniumdiolate siderophores, megapolibactins and plantaribactin were fully characterized. In vitro assays and in vivo monitoring experiments revealed that the iron chelators also liberate nitric oxide (NO) in plant roots. This finding is important since NO donors are considered as biofertilizers that maintain iron homeostasis and increase overall plant fitness.

Authors: R. Hermenau, J. L. Mehl, K. Ishida, B. Dose, S. J. Pidot, T. P. Stinear, C. Hertweck

Date Published: 9th Sep 2019

Publication Type: Journal

GNPS-guided discovery of xylacremolide C and D, evaluation of their putative biosynthetic origin and bioactivity studies of xylacremolide A and B.

Abstract (Expand)

Targeted HRMS(2)-GNPS-based metabolomic analysis of Pseudoxylaria sp. X187, a fungal antagonist of the fungus-growing termite symbiosis, resulted in the identification of two lipopeptidic congeners of … xylacremolides, named xylacremolide C and D, which are built from d-phenylalanine, l-proline and an acetyl-CoA starter unit elongated by four malonyl-CoA derived ketide units. The putative xya gene cluster was identified from a draft genome generated by Illumina and PacBio sequencing and RNAseq studies. Biological activities of xylacremolide A and B were evaluated and revealed weak histone deacetylase inhibitory (HDACi) and antifungal activities, as well as moderate protease inhibition activity across a panel of nine human, viral and bacterial proteases.

Authors: F. Schalk, J. Fricke, S. Um, B. H. Conlon, H. Maus, N. Jager, T. Heinzel, T. Schirmeister, M. Poulsen, C. Beemelmanns

Date Published: 24th May 2021

Publication Type: Journal

Gramibactin is a bacterial siderophore with a diazeniumdiolate ligand system.

Abstract (Expand)

Genome mining and chemical analyses revealed that rhizosphere bacteria (Paraburkholderia graminis) produce a new type of siderophore, gramibactin, a lipodepsipeptide that efficiently binds iron with a … logbeta value of 27.6. Complexation-induced proton NMR chemical shifts show that the unusual N-nitrosohydroxylamine (diazeniumdiolate) moieties participate in metal binding. Gramibactin biosynthesis genes are conserved in numerous plant-associated bacteria associated with rice, wheat, and maize, which may utilize iron from the complex.

Authors: R. Hermenau, K. Ishida, S. Gama, B. Hoffmann, M. Pfeifer-Leeg, W. Plass, J. F. Mohr, T. Wichard, H. P. Saluz, C. Hertweck

Date Published: 1st Aug 2018

Publication Type: Journal

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