A Biosynthetic and Taxonomic Atlas of the Global Lichen Holobiont.

Lichens are pioneer species in several ecosystems, and as such are found in a variety of geographic regions and environments. Here, inspection of metagenomic data from 794 lichen samples from 34 countries reveals the presence of a complex holobiont harbouring remarkable biosynthetic capabilities, particularly in the bacterial consortia, a component that has been somewhat underappreciated. While bacteria were consistently present, their abundance varied among lichen taxa. Common bacterial genera included Microbacterium, Terribacillus, and JABEUN01 (an Acidimicrobiaceae bacterium awaiting Latin binomial naming assignment) albeit in low abundance. Lichenihabitans and Sphingomonas genera were moderately abundant, present in approximately 30% of samples, and exhibited an enrichment in the number of biosynthetic gene clusters (BGCs) predicted to encode secondary metabolites (biosynthetic potential). We found that both fungal and bacterial biosynthetic repertoires appeared to follow genus-specific patterns but that there was greater relative homogeneity of BGCs in the fungal genera. The substantial biosynthetic diversity within lichen holobionts is evident in our findings, with the lichen-associated bacteria emerging as a promising potential source for sustainable drug discovery.