Isolation And Identification Of Cultural Fungi In The Sediments Below Ocean Floor And Their Nitrification And Denitrification Abilities

Ocean accounts for about 71%of the earth's surface area and plays a vital role in the earth's material cycle.The implementation of the Ocean Drilling Program(ODP)and the Integrated Ocean Drilling Program(Integrated Ocean Drilling Program,IODP)laid the foundation for the study of the composition of the deep biosphere in the ocean bottom and its role in the earth's material cycle.In this study,the cultivated fungi were isolated and identified from 28 sediments(rocks)from IODP 337(2012),and their nitrification and denitrification abilities were preliminarily studied in order to understand the diversity of the cultivated fungi in the deep biosphere and their role in the deep environmental nitrogen cycle.The main results are as follows:1.By using the solid plate culture method of artificial sea water culture medium,2 fungi,7 genera and 31 strains of Ascomycota and Basidiomycetes were isolated from 28 sediments below the ocean floor.There are 6 genera and 30 strains of Ascomycota:Aspergillus,Aureobasidium,Eurotium,Hamigera,Penicillium and Cladosporium,1 species of Basidiomycetes:Termitomyces cartilagineus.There were 13 strains of Penicillium and 7 strains of Aspergillus,which accounted for 41.9%and 22.6%of the total number of isolated fungi,indicating that Penicillium and Aspergillus were the dominant fungi in this separation sample;this result was consistent with the conclusion obtained from the same source samples early in the laboratory.However,2 genera and 6 strains were not isolated from the previous studies.They were Hamigera(5 strains)and Termitomyces(1 strain).2.The comparison and similarity analysis of the ITS and 28S rRNA gene sequences of 27 species and 69 strains of fungi isolated from the previous and this separate laboratory showed that the sequence similarity between the isolated strains and the same species in the terrestrial environment was very high,both greater than 97%.It is speculated that deep sea sediment fungi are likely to come from land3.The nitrification of 12 kinds of subseafloor fungi under anaerobic conditions was studied with NH4+as the sole substrate.The results showed that all of these fungi had the nitrification of transforming NH4+ into NO3-,of which the nitrification of Schizophyllum commune 20R-7-F01 was the strongest;The difference of denitrification between the strains of different sources was compared,and the homology analysis and cluster analysis were used to further verify that the fungi in the deep sediments below the ocean floor may be derived from the land4.15N isotopic markers and GC-MS methods were used to study the denitrification of 7 subseafloor fungi in situ under anaerobic conditions.It was found that a strain of Aspergillus sydowii 8L-9-F02,separated from 1.6 kmbsf,had complete denitrification with the conversion of sodium nitrate into nitrogen.After eliminating the possibility of contamination of prokaryotic microorganisms,it is further confirmed that the fungi do have anaerobic denitrification.This discovery has not been reported before,breaking the knowledge that denitrifying fungi can only form N2O rather than under anaerobic conditions with HNO3 or HNO2 as the sole nitrogen sourceTo be summarized,fungi,an important component of the deep biosphere of the ocean floor,have rich diversity and very strong environmental adaptability,and may play an important role in the biogeochemical cycle of the deep environment below the ocean floor.