Fungal community analysis in seawater of the Mariana Trench as estimated by Illumina HiSeq

Abstract

This study assessed the diversity and distribution of fungal communities in thirteen marine seawater samples from four sites (L1, L3, L4 and L7) of the Mariana Trench, with a depth range of 1000-4000 meters, using Illumine Hiseq sequencing with fungal-specific primers targeting the internal transcribed spacer (ITS) region of the ribosomal rRNA gene. Sedimentary fungal communities showed high diversity with 209 880 reads belonging to 91 operational taxonomic units (OTUs). Of these OTUs, 45 belonged to the Ascomycota, 37 to Basidiomycota, 3 to Chytridiomycota, 1 to Glomeromycota, 1 to Cryptomycota, and 4 to unknown fungi. The major fungal orders included Saccharomycetales and Sporidiobolales. The commonly found fungal genera were Candida, Malassezia and Cryptococcus. These results suggest the existence of diverse fungal communities in the Mariana Trench marine seawater, which can be considered as a useful community model for further ecological and evolutionary study of fungi in the trench.

Fig. 1. Map of Mariana Trench showing the sites where seawater samples were collected in this study. Four sampling sites are indicated by red dots.

Fig. 2. The taxonomic distribution of 91 OTUs at the phylum and order level.

Fig. 3. Gephi network diagrams illustrating the fungal OTUs recovered from seawater samples taken from the same sampling sites. (a) 79 OTUs occurring within M1.1, M1.2, M1.3 and M1.4 of the sampling site L1 (blue color); (b) 75 OTUs occurring within M3.1, M3.2 and M3.4 of the sampling site L3 (red color); (c) 74 OTUs occurring within M4.3, M4.3 and M4.4 of the sampling site L4 (green color); (d) 82 OTUs occurring within M7.1, M7.2 and M7.3 of the sampling site L7 (purple color).

Fig. 4. Gephi network diagrams illustrating the fungal OTUs recovered from seawater samples with same water depths. (a) 86 OTUs occurring within M1.1, M3.1 and M7.1 samples; (b) 73 OTUs occurring within M1.2, M3.2, M4.2 and M7.2 samples; (c) 65 OTUs occurring within regions of the M1.3, M4.3 and M7.3 samples; (d) 69 OTUs occurring within regions of the M1.4, M3.4 and M4.4 samples; blue color dot represent samples from L1; red color dot represent samples from L3, green color dot represent samples from L4, purple color dot represent samples from L7.