Unveiling Concealed Functions of Endosymbiotic Bacteria Harbored in the Ascomycete Stachylidium bicolor

Among the plethora of unusual secondary metabolites isolated from are the tetrapeptidic endolides A and B. Both tetrapeptides contain 3-(3-furyl)-alanine residues, previously proposed to originate from bacterial metabolism. Inspired by this observation, we aimed to identify the presence of endosymbi...

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Bibliographic Details
Published in:Applied and environmental microbiology 2018-08, Vol.84 (15)
Main Authors: Almeida, Celso, Silva Pereira, Cristina, Gonzalez-Menendez, Victor, Bills, Gerald, Pascual, Javier, Sánchez-Hidalgo, Marina, Kehraus, Stefan, Genilloud, Olga
Format: Article
Language:English
Subjects:
Alanine
Bacteria
Biofilms
Burkholderia contaminans
Conidia
Endosymbionts
Eukaryotes
Fungi
Gene sequencing
Latency
Metabolism
Metabolites
Microbial Ecology
Microbiology
rRNA 16S
Secondary metabolites
Sphingomonas
Sporulation
Spotlight
Symbiosis
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Summary:Among the plethora of unusual secondary metabolites isolated from are the tetrapeptidic endolides A and B. Both tetrapeptides contain 3-(3-furyl)-alanine residues, previously proposed to originate from bacterial metabolism. Inspired by this observation, we aimed to identify the presence of endosymbiotic bacteria in and to discover the true producer of the endolides. The endobacterium was initially detected by 16S rRNA gene amplicon sequencing from the fungal metagenome and was subsequently isolated. It was confirmed that the tetrapeptides were produced by the axenic only when in latency. Fungal colonies unable to produce conidia and the tetrapeptides were isolated and confirmed to be free of A second endosymbiont identified as related to was also isolated. imaging of the mycelium supported an endosymbiotic relationship between and the two endobacteria. Besides the technical novelty, our analyses revealed that the two endobacteria are compartmentalized in defined fungal cells, prevailing mostly in latency when in symbiosis. Within the emerging field of intracellular bacterial symbioses, fungi are the least studied eukaryotic hosts. Our study further supports the Fungi as a valuable model for understanding endobacterial symbioses in eukaryotes. The discovery of two bacterial endosymbionts harbored in mycelium, and , is described here. Production of tetrapeptides inside the mycelium is ensured by , and fungal sporulation is influenced by the endosymbionts. Here, we illustrate the bacterial endosymbiotic origin of secondary metabolites in an Ascomycota host.
ISSN:0099-2240
1098-5336
DOI:10.1128/aem.00660-18