Microbial community associated with the crustose lichen Rhizocarpon geographicum L. (DC.) living on oceanic seashore: A large source of diversity revealed by using multiple isolation methods

Abstract

Recently, the study of the interactions within a microcosm between hosts and their associated microbial communities drew an unprecedented interest arising from the holobiont concept. Lichens, a symbiotic association between a fungus and an alga, are redefined as complex ecosystems considering the tremendous array of associated microorganisms that satisfy this concept. The present study focuses on the diversity of the microbiota associated with the seashore located lichen Rhizocarpon geographicum, recovered by different culture-dependent methods. Samples harvested from two sites allowed the isolation and the molecular identification of 68 fungal isolates distributed in 43 phylogenetic groups, 15 bacterial isolates distributed in five taxonomic groups and three microalgae belonging to two species. Moreover, for 12 fungal isolates belonging to 10 different taxa, the genus was not described in GenBank. These fungal species have never been sequenced or described and therefore non-studied. All these findings highlight the novel and high diversity of the microflora associated with R. geographicum. While many species disappear every day, this work suggests that coastal and wild environments still contain an unrevealed variety to offer and that lichens constitute a great reservoir of new microbial taxa which can be recovered by multiplying the culture-dependent techniques.

Volatile Organic Compounds from a Lichen-Associated Bacterium, Paenibacillus etheri, Interact with Plant-Parasitic Cyst Nematodes

“…We previously isolated Paenibacillus etheri from the lichen Rhizocarpon geographicum , and it appeared that the strain represented 62.5% of total bacterial isolates. 23 Looking closer, on the lichen surface, we have also observed microscopically a bacteriophage nematode. Indeed, the existence of various invertebrates inhabiting lichens such as arthropods or nematodes is well established, 24 , 25 while within different genera sheltered, Paenibacillus was identified as “protectors” in the lichen holobiont.…”

“…Furthermore, Paenibacillus species can also be harbored in lichens, , a symbiotic association between a fungal (mycobiont) and an algal (photobiont) partner and where a rich microflora occurs. We previously isolated Paenibacillus etheri from the lichen Rhizocarpon geographicum, and it appeared that the strain represented 62.5% of total bacterial isolates . Looking closer, on the lichen surface, we have also observed microscopically a bacteriophage nematode.…”

Rhizocarpon geographicumlichen discloses a highly diversified microbiota carrying antibiotic resistance and Persistent Organic Pollutants tolerance

“…Firstly, Bjelland et al [20], through a 16S rDNA metabarcoding approach investigated the diversity of bacterial communities associated with R. geographicum without combining culturing methods. Secondly, a recent study from Miral et al [63] isolated 24 bacteria strains and 68 fungal isolates from R. geographicum by using classical microbiological media. Miral and co-authors did not use antifungal compounds for bacterial isolation and by consequence they isolated a low bacterial diversity.…”

“…Secondly, a recent study from Miral et al . [63] isolated 24 bacteria strains and 68 fungal isolates from R. geographicum by using classical microbiological media. Miral and co-authors did not use antifungal compounds for bacterial isolation and by consequence they isolated a low bacterial diversity.…”

Eremoxylarins D–J, Antibacterial Eremophilane Sesquiterpenes Discovered from an Endolichenic Strain of Xylaria hypoxylon

“…7,8 In a previous study, we obtained 68 fungal isolates distributed in 43 phylogenetic groups from the crustaceous lichen Rhizocarpon geographicum collected in Finistere, France. 9 During the isolation process, one species, Xylaria hypoxylon, exhibited interesting antagonistic interactions with other fungi such as Dendrothyrium variisporum. X. hypoxylon is known to occupy different ecological niches with a wide host range and a widespread global occurrence.…”