Unexpected diverse fungal symbionts revealed by deep sequencing of sponge microbiome

Compared with the understanding of sponge bacterial and archaeal symbionts, the diversity of fungal symbionts of sponges remains largely unknown. In this study, the communities of fungal symbionts in two sponges Holoxea sp. and Lamellomorpha sp. were revealed for the first time by the total metagenome DNA-based Illumina GAIIx pyrosequencing of sponge microbiome. This study revealed the highest diversity of sponge fungal symbionts including eight phyla and four subphyla. In particular, Blastocladiomycota, Chytridiomycota, Glomermycota, Neocallimastigomycota, Microsporidia, Kickxellomycotina, Zoopagomycotina and Entomophthoromycotina were detected in sponges for the first time. Except Microsporidia, which was observed in Lamellomorpha sp. only, the other seven phyla fungi were common in both sponges. On order level, 50 and 52 fungal orders were detected in Holoxea sp. and Lamellomorpha sp., respectively, with 38 shared fungal orders, especially 48 fungal taxa (47 orders and one division) were detected in marine sponges for the first time. The revealed unexpected diversity of marine fungal symbionts of sponges drastically extends our knowledge about eukaryotic symbionts with sponges.