全球表层土壤中微生物群落的结构及功能

土壤中存在着地球上最多样化的微生物群落,它们对地球养分循环和碳储存都至关重要。为了更好的了解土壤功能,对土壤微生物的全球分布模式和功能基因序列进行建模,并了解土壤中细菌和真菌群落的多样性和结构之间的生物、环境联系是很有必要的。

Identifying the ‘unidentified’ fungi: a global-scale long-read third-generation sequencing approach

Molecular identification methods,in particular high-throughput sequencing tools,have greatly improved our knowledge about fungal diversity and biogeography,but many of the recovered taxa from natural environments cannot be identified to species or even higher taxonomic levels.This study addresses the phylogenetic placement of previously unrecognized fungal groups by using two complementary approaches:(i)third-generation amplicon sequencing analysis of DNA from global soil samples,screening out ITS reads of<90%similarity to other available Sanger sequences,and(ii)analysis of common fungal taxa that were previously indicated to be enigmatic in terms of taxonomic placement based on the ITS sequences alone(so-called top50 sequences).For the global soil samples,we chose to amplify the full rRNA gene operon using four partly overlapping amplicons and multiple newly developed primers or primer combinations that cover nearly all fungi and a vast majority of non-fungal eukaryotes.We extracted the rRNA 18S(SSU)and 28S(LSU)genes and performed phylogenetic analyses against carefully selected reference material.Both SSU and LSU analyses placed most soil sequences and top50 sequences to known orders and classes,but tens of monophyletic groups and single sequences remained outside described taxa.Furthermore,the LSU analyses recovered a few small groups of sequences that may potentially represent novel phyla.We conclude that rRNA genes-based phylogenetic analyses are efficient tools for determining phylogenetic relationships of fungal taxa that cannot be placed to any order or class using ITS sequences alone.However,in many instances,longer rRNA gene sequences and availability of both SSU and LSU reads are needed to improve taxonomic resolution.By leveraging third-generation sequencing from global soil samples,we successfully provided phylogenetic placement for many previously unidentified sequences and broadened our view on the fungal tree of life,with 10-20%new order-level taxa.In addition,the PacBio sequence data greatly extends fungal class-level information in reference databases.

The Global Soil Mycobiome consortium dataset for boosting fungal diversity research

Fungi are highly important biotic components of terrestrial ecosystems,but we still have a very limited understanding about their diversity and distribution.This data article releases a global soil fungal dataset of the Global Soil Mycobiome consortium(GSMc)to boost further research in fungal diversity,biogeography and macroecology.The dataset comprises 722,682 fungal operational taxonomic units(OTUs)derived from PacBio sequencing of full-length ITS and 18S-V9 variable regions from 3200 plots in 108 countries on all continents.The plots are supplied with geographical and edaphic metadata.The OTUs are taxonomically and functionally assigned to guilds and other functional groups.The entire dataset has been corrected by excluding chimeras,index-switch artefacts and potential contamination.The dataset is more inclusive in terms of geographical breadth and phylogenetic diversity of fungi than previously published data.The GSMc dataset is available over the PlutoF repository.