Diversity And Distribution Of Fungal Communities In The Marine Sediments Of Shenzhen Bay

Microorganisms are widely distributed among marine environment and play an important role in marine ecosystems.Due to the special physical and chemical conditions,there were few study of concern on the marine microorganisms.Comparing with bacteria and archaea,marine fungi only received limited attention.The purpose of the present study was to understand the diversity and distribution of the marine fungi in sediments of Shenzhen Bay by using culture-dependent technique,Miseq high-throughput sequencing technology and real-time quantitative PCR.The meta-genomic DNA was amplified for the ITS2 tags,and then sequenced by high-throughput sequencing.A total of 1,084,873 tags were clustered into 1,370 OTUs with the 97%similarity cut-off.Of these OTUs,572(43.97%)can be determined to the phylum level,376(28.90%)to class level,245(18.83%)to genus level,belonging to 5 phyla,18 classes and 161 genera.The phylum with the mean of relative abundance above 1%in all samples was defined as key phylum.The key phyla were Ascomycota and Basidiomycota and the relative abundance were 47.5%and 32.7%.Comparing the relative abundance with all samples in phylum level,the result showed that the difference was not only between the position of the sampling sites but also between the depth of that.We also identified the key genera by the mean of relative abundance above 1%in all samples,and it was found that the key genera in Shenzhen Bay were 10 genera,including Meyerozyma.Trichoderma,Talaromyces,Paraconiothyrium,Scedosporium,Cladosporium.Paraphaeosphaeria,Roussoell and Cystobasidium,belong to Ascomycota and Basidiomycota.These key genera can be further classified into 4 classes in Ascomycota(Saccharomycetes,Sordariomycetes,Eurotiomycetes and Dothideomycetes)and 1 class in Basidiomycota(Cystobasidiomycetes).The abundance of the ITS rRNA gene in the sediments of Shenzhen Bay was detected between 1.85±0.32×104 to 1.10±0.07×106 copies/g sediment by fluorescence quantitative PCR.A total of 38 fungal isolates were recovered from 10 sample sites.The strains were identified by morphological identification and ITS sequencing,all the strains belong to Ascomycota and Basidiomycota and the Ascomycota are the dominant phylum.The strains belong to 6 classes(25 genera)including Eurotiomycetes,Dothideomycetes,Sordariomycetes,Saccharomycetes,Agaricomycete and Microbotryomycetes all the classes were also founded by culture-independent method.The dominant genera are Meyerozyma,Penicillium and Aspergillus accounting for more than 40%of the total isolated fungus strains.More than 50%of the isolated strains belong to the 13 genera observed at both culture-dependent and culture-independent method.This study on the marine fungi diversity and abundance in sediments of Shenzhen Bay shows that there are abundant fungi resource in the marine environment,and many unknown fungi remain to be found.The results of this thesis might provide a better understanding of the diversity and distribution of the marine fungi and provides important basic theory for the development,utilization and the study of marine fungi in marine ecosystem.