Jebaraj Cathrine Sumathi, Forster Dominik, Kauff Frank, Stoeck Thorsten
National Institute of Oceanography, Council of Scientific and Industrial Research, Dona Paula, 403 004, Goa, India,
Prog Mol Subcell Biol. 2012;53:189-208. doi: 10.1007/978-3-642-23342-5_10.
Molecular diversity surveys of marine fungi have demonstrated that the species richness known to date is just the tip of the iceberg and that there is a large extent of unknown fungal diversity in marine habitats. Reports of novel fungal lineages at higher taxonomic levels are documented from a large number of marine habitats, including the various marine oxygen-deficient environments (ODEs). In the past few years, a strong focus of eukaryote diversity research has been on a variety of ODEs, as these environments are considered to harbor a large number of organisms, which are highly divergent to known diversity and could provide insights into the early eukaryotic evolution. ODEs that have been targeted so far include shallow water sediments, hydrothermal vent systems, deep-sea basins, intertidal habitats, and fjords. Most, if not all, molecular diversity studies in marine ODEs have shown, that contrary to previous assumptions, fungi contribute significantly to the micro-eukaryotic community in such habitats. In this chapter, we have reanalyzed the environmental fungal sequences obtained from the molecular diversity survey in 14 different sites to obtain a comprehensive picture of fungal diversity in these marine habitats. The phylogenetic analysis of the fungal environmental sequences from various ODEs have grouped these sequences into seven distinct clades (Clade 1-7) clustering with well-known fungal taxa. Apart from this, four environmental clades (EnvClade A, B, C, and D) with exclusive environmental sequences were also identified. This has provided information on the positioning of the environmental sequences at different taxonomic levels within the major fungal phylums. The taxonomic distribution of these environmental fungal sequences into clusters and clades has also shown that they are not restricted by geographical boundaries. The distribution pattern together with the reports on the respiratory abilities of fungi under reduced oxygen conditions shows that they are highly adaptive and may have a huge ecological role in these oxygen deficient habitats.
海洋真菌的分子多样性调查表明，迄今为止已知的物种丰富度只是冰山一角，海洋栖息地中存在大量未知的真菌多样性。在包括各种海洋缺氧环境（ODEs）在内的大量海洋栖息地中，都有关于更高分类水平上新真菌谱系的报道。在过去几年中，真核生物多样性研究的一个重点是各种ODEs，因为这些环境被认为蕴藏着大量生物，它们与已知多样性高度不同，可能为早期真核生物进化提供见解。目前已针对的ODEs包括浅水沉积物、热液喷口系统、深海盆地、潮间带栖息地和峡湾。大多数（如果不是全部的话）海洋ODEs中的分子多样性研究表明，与先前的假设相反，真菌对这些栖息地中的微型真核生物群落有重大贡献。在本章中，我们重新分析了从14个不同地点的分子多样性调查中获得的环境真菌序列，以全面了解这些海洋栖息地中的真菌多样性。对来自各种ODEs的真菌环境序列进行的系统发育分析已将这些序列分为七个不同的进化枝（进化枝1 - 7），它们与已知的真菌类群聚类。除此之外，还鉴定出了四个具有独特环境序列的环境进化枝（环境进化枝A、B、C和D）。这提供了关于环境序列在主要真菌门内不同分类水平上的定位信息。这些环境真菌序列在聚类和进化枝中的分类分布也表明它们不受地理边界的限制。这种分布模式以及关于真菌在低氧条件下呼吸能力的报道表明，它们具有高度适应性，可能在这些缺氧栖息地中发挥巨大的生态作用。
