Obligate anaerobic fungi of the phylum Neocallimastigomycota play a key role in digesting fibrous feeds in the gut of herbivores, but little is known about their global diversity. In this study, the collective diversity of gut anaerobic fungi was examined using all curated internal transcribed spacer 1 (ITS1) sequences of anaerobic gut fungi available in GenBank. The 262,770 quality-checked fungal ITS1 sequences downloaded from GenBank were assigned to 274 operational taxonomic units (OTUs) at the approximate species level. Of these approximate species-equivalent (Sp-eq) OTUs, 119 were represented by at least five ITS1 sequences, with 38 containing known species and 81 containing no known species. Based on a rarefaction analysis, the currently available ITS1 sequences represent nearly all the major species of gut anaerobic fungi, but much more sequencing effort is needed to assess the actual richness of minor OTUs. One dataset of ITS1 reference sequences (referred to as AF-RefSeq) and one comprehensive taxonomic framework are also presented, and they are shown to be suitable for taxonomic classification of most of the ITS1 sequences in GenBank. The results of the present study may help guide future studies involving taxonomic and phylogenetic analysis of ITS1 sequences of anaerobic fungi and targeted isolation and characterization of new anaerobic fungi.

中文翻译：

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肠道厌氧真菌全球多样性的系统进化普查和新的分类学框架

在门的专厌氧真菌Neocallimastigomycota在消化草食动物肠道中的纤维性饲料中起关键作用，但对其全球多样性知之甚少。在这项研究中，使用GenBank中提供的所有精选的厌氧肠道真菌的内部转录间隔区1（ITS1）序列检查了肠道厌氧真菌的集体多样性。从GenBank下载的262,770个经过质量检查的真菌ITS1序列被分配给了近似物种级别的274个操作生物分类单位（OTU）。在这些近似的物种等效（Sp-eq）OTU中，至少有五个ITS1序列代表119个，其中38个包含已知物种，而81个不包含已知物种。根据稀有度分析，目前可用的ITS1序列几乎代表了肠道厌氧真菌的所有主要物种，但是需要更多的测序工作来评估次要OTU的实际丰富度。还介绍了一个ITS1参考序列的数据集（称为AF-RefSeq）和一个完整的分类框架，显示它们适用于GenBank中大多数ITS1序列的分类。本研究的结果可能有助于指导有关厌氧真菌ITS1序列的分类学和系统发育分析以及新厌氧真菌的靶向分离和表征的未来研究。