Fungal Molecular Diversity In Marine Sediments Collected From The Yellow Sea And Bohai Sea

Marine sediments samples were collected from the Bohai and Yellow Sea in Jun,2013. Metagenomic DNA was extracted, and analyzed by high-throughput454pyrosequencing. ITS1and ITS2were used as metabarcodes for fungi. High-qualityreads were clustered into operational taxonomic units (OTUs) according to97%sequence similarity. Community Similarity and fungal diversity are studied atdifferent sea areas and taxonomic levels. Several physio-chemical parameters aremeasured for each sample, including total organic carbon content (TOC), totalnitrogen content (TN), C:N ratio (C/N), total phosphorate content (TP), total sulphurcontent (TS), total potassium content (TK), pH and average particle size. The partialcorrelation analyses are perfprmed to explore the relationships between fungaldiversity and environmental variables. The correlations between environmentalvariables and fungal community compositions are investigated by redundancyanalysis (RDA) with the most significant environmental parameters recognized.Data reveal unexpected hyperdiversity of sedimental fungi and meanwhile aplethora of phylotypes in the Yellow Sea and Bohai Sea. No less than122,211ITS1reads with sufficient quality are obtained from30samples, of which76.98%areidentified at genus level. A total of3,714OTUs,290phylotypes, belonging to257genera are discovered. Based on ITS2pyrosequencing,119,776reads with sufficientquality are obtained from30samples, of which87.91%are identified at genus level.A total of6,676OTUs,232phylotypes, belonging to201genera are detected. At the order level, fungal abundance based on the average OTUs is compared forthree sea areas. ITS1analysis indicates that fungal OTUs in the South Yellow Seasignificantly overnumber those of the North Yellow Sea and Bohai Sea. OTUsdetected in the North Yellow Sea significantly overnumber those in the Bohai Sea.ITS2analysis reveals the contrary result among three sea areas, and no significantdifference is discovered between the North Yellow Sea and Bohai Sea.At the phylum level, number of fungal OTUs in different sea areas is compared.There is no significant difference in ascomycetes of three sea areas. ITS1analysisshows the basidiomycetes in the North Yellow Sea significantly outnumber those inthe Bohai Sea, which is contrary to the ITS2-based conclusion. ITS2analysis suggeststhe Glomeromycota OTUs discovered in the Bohai and North Yellow Sea aresignificant more than those of the North Yellow Sea, while the ITS1-based analysisshows no significant difference in three sea areas.Fungal distribution pattern analyses based on ITS1and ITS2make the similarconclusions. ITS1analysis indicates that fungal OTUs in the Yellow Sea clumped andrandomly distribute in the Bohai Sea. ITS2analysis shows that fungal OTUs in theNorth Yellow Sea clumped. Fungal phylotypes randomly distribute in three sea areas.There is no significant difference observed between Shannon-Wiener indice for anytwo sea areas. Sordariomycetes and Dothideomycetes are the most dominant classes,followed by Agaricomycetes.Sediment samples from the same sea area tend to have the similar fungalcommunity structure. From low latitude to high, fungal diversity changes from high tolow correspondingly. The Sorth Yellow Sea has the highest sedimental fungaldiversity. The fungal community was influenced primarily by TN, followed by C/Nand pH.Although ITS1and ITS2yield a similar taxonomic composition at the phylum and class level, some differences are remarkably noted. PCR stochasticity and primerbias cannot be excluded as important causes for the differences. In this study, the pairof primers ITS1F/ITS2used for the amplification of the ITS1region produced lessnon-fungal sequences in addition to a higher number of sequences than the pairamplifying the ITS2region. ITS1is on average somewhat more variable than ITS2inmost fungal lineages. ITS1is recommended in priority as metabarcode for fungibased on the present study. We propose a strategy for assessment of fungalbiodiversity with ITS1and ITS2metabarcodes combined together to draw a morecomplete and reliable picture of environmental fungi. In addition, the treatments ofsingletons and doubletons should be considered in order to reduce errors and artifacts.While molecular ecology provides a powerful tool of environmentalmicrobiology, species identification has a paramount importance. In this study, threenew fungi (including Phaeoisaria sedimenticola、Ascotricha longipila、Ascotrichaparvispora) and one new combination (Ascotricha sinuosa) are introduced anddescribed based on morphological characteristics and phylogenetic analyses. Inaddition, the phylogeny of Ascotricha and its anamorphs are further explored. Resultsindicate that Ascotricha belong to Xylariaceae, Xylarioideae. Dicyma is anamorphicAscotricha, and Hansfordia, as an allied genus with Dicyma, may also haverelationship with Ascotricha.