Posidonia oceanica a dominant herb of marine grassland from the Mediterranean has been selected for this project as a unique model system for studying its microbiota. This species is known for its longevity and is potentially the host for a large endophyte community (1). The aim of the project was to comprehensively profile the endophyte community of this peculiar marine plant, use it as a model for deciphering microbiome interactions and investigate if this can inspire the discovery of new antibacterial agents.
The diversity of endophytic microbial communities from leaves and rhizomes was assessed by high throughput sequencing approaches and 23 strains of fungi and bacteria were isolated and identified. These strains were cultivated and extracted by ethyl acetate for metabolite profiling and antimicrobial activity screening.
All samples were dereplicated by UHPLC-HRMS/MS and molecular networking for a preliminary survey of their secondary metabolite composition. Surprisingly some of the screened species presented unexpected high amounts of fatty acids. Among all fungal strains Lulwoana sp. were found very specific to the marine environment. Their metabolite profiles reveal the presence of original corymbiferan lactones and their targeted isolation reveal the presence of a new methylated derivative. Extensive profiling in different cultivation media also demonstrated the diversity of such compounds in these endophytes.
In parallel the extracts were screened for their antimicrobial activity against Staphylococcus aureus, Propionibacterium acnes and Pseudomonas aeruginosa. Penicillium and Fusarium spp. strains were found to display interesting antimicrobial activities and a correlation between their chemical profiles and activities will be presented.
All the results obtained provide a first survey of chemical and bioactivity profiles in view of studying interactions between the members of this unique community.
Acknowledgement
This work has benefited from a SECIL grant from ANR (15-CE21-0016) and SNF (310030E-164289/1).
Reference
- Vohník M, et al. Mycorrhiza. 2015;25(8):663-72.