Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada.
Merton College, University of Oxford, Oxford, United Kingdom.
PLoS One. 2021 Mar 24;16(3):e0247594. doi: 10.1371/journal.pone.0247594. eCollection 2021.
Snow and ice present challenging substrates for cellular growth, yet microbial snow communities not only exist, but are diverse and ecologically impactful. These communities are dominated by green algae, but additional organisms, such as fungi, are also abundant and may be important for nutrient cycling, syntrophic interactions, and community structure in general. However, little is known about these non-algal community members, including their taxonomic affiliations. An example of this is Chionaster nivalis, a unicellular fungus that is morphologically enigmatic and frequently observed in snow communities globally. Despite being described over one hundred years ago, the phylogeny and higher-level taxonomic classifications of C. nivalis remain unknown. Here, we isolated and sequenced the internal transcribed spacer (ITS) and the D1-D2 region of the large subunit ribosomal RNA gene of C. nivalis, providing a molecular barcode for future studies. Phylogenetic analyses using the ITS and D1-D2 region revealed that C. nivalis is part of a novel lineage in the class Tremellomycetes (Basidiomycota, Agaricomycotina) for which a new order Chionasterales ord. nov. (MB838717) and family Chionasteraceae fam. nov. (MB838718) are proposed. Comparisons between C. nivalis and sequences generated from environmental surveys revealed that the Chionasterales are globally distributed and probably psychrophilic, as they appear to be limited to the high alpine and arctic regions. These results highlight the unexplored diversity that exists within these extreme habitats and emphasize the utility of single-cell approaches in characterizing these complex algal-dominated communities.
雪和冰是对细胞生长极具挑战性的基质，但微生物雪群落不仅存在，而且具有多样性和生态影响力。这些群落主要由绿藻主导，但也有其他生物，如真菌，同样丰富，它们可能对养分循环、共生相互作用和群落结构具有重要意义。然而，对于这些非藻类的群落成员，包括它们的分类学归属，人们知之甚少。Chionaster nivalis 就是一个例子，这是一种单细胞真菌，形态奇特，在全球范围内的雪群落中经常被观察到。尽管早在一百多年前就已被描述，但 C. nivalis 的系统发育和高级分类学分类仍然未知。在这里，我们分离并测序了 C. nivalis 的内部转录间隔区 (ITS) 和大亚基核糖体 RNA 基因的 D1-D2 区，为未来的研究提供了分子条码。使用 ITS 和 D1-D2 区进行的系统发育分析表明，C. nivalis 是 Tremellomycetes 纲（担子菌门，伞菌纲）中新谱系的一部分，因此提议了一个新的 Order Chionasterales ord. nov. (MB838717) 和新的科 Chionasteraceae fam. nov. (MB838718)。C. nivalis 与环境调查中生成的序列之间的比较表明，Chionasterales 是全球分布的，可能是嗜冷的，因为它们似乎仅限于高海拔和北极地区。这些结果突出了这些极端生境中存在的未被探索的多样性，并强调了单细胞方法在描述这些以藻类为主的复杂群落中的实用性。
