Fungal diversity in deep-sea sediments – the presence of novel fungal groups

We investigated the diversity of fungal communities in 10 different deep-sea sediment samples by PCR-mediated internal transcribed spacer (ITS) regions of rRNA gene clone analysis. Although some of the amplified sequences were identified as common terrestrial fungal species, the majority were novel sequences that were not closely related to previously identified fungal ITS sequences in public databases. Phylogenetic analysis also suggested the novel phylogenetic affiliation of a group of predominant deep-sea phylotypes within the phylum Ascomycota. These phylotypes may be distributed widely in global deep-sea sediments. Another novel phylotype was placed in deep branches within the phylum Chytridiomycota with Rozella spp. as the closest related organisms. This study revealed the possible existence of previously unknown fungal components in various depths and sites of deep-sea sedimentary habitats. It is suggested that deep-sea environments are habitats hosting previously unexplored fungi, which may provide key insights into the early evolution of fungi and their ecological and physiological significance.