Diversity of organism in the Usnea longissima lichen

Lichens are self-supporting and ecologically obligate associations between symbiotic fungi, commonly an Ascomycete (mycobiont), and a photosynthesising organism (photobiont). Samples of Usnea longissima lichen were collected from Abies georgei in the Pudacuo National Park, Shangri-la County, Yunan Province, China, and their biological compositions were analysed by cultural and metagenomic approaches. We found that the Usnea longissima lichen symbiont contained a number of endolichenic fungi. The organisms identified included Usnea, Sydowia, Alectoria, Punctelia, Penicillium, Mucor, Hypocrea, Trichoderma, Elaphocordyceps, Arthrinium and Cladosporium. This is the first report of different genera of lichenized fungi, Usnea, Alectoria and Punctelia, co-existing in the same symbiont. This may be related to multiple origins for the fungi lichen symbiosis. Using algal-specific ITS rDNA primers, the photobiont of the Usnea longissima lichen was identified as Trebouxia. However, we also found that Poterioochromonas was present in the Usnea longissima lichen, through 18S rDNA clonal analysis of the metagenome. To date, there has been no report of two cross-phylum algae co-existing in a single lichen. This study provides new insight into the biological composition of the lichen Usnea longissima, highlighting its microbial diversity.