1] Department of Genetics, Centre for Microbial Ecology and Genomics, University of Pretoria, Pretoria, South Africa [2] Institute for Microbial Biotechnology and Metagenomics, University of the Western Cape, Cape Town, South Africa.
ISME J. 2013 Nov;7(11):2080-90. doi: 10.1038/ismej.2013.94. Epub 2013 Jun 13.
Hypoliths (cryptic microbial assemblages that develop on the undersides of translucent rocks) are significant contributors to regional C and N budgets in both hot and cold deserts. Previous studies in the Dry Valleys of Eastern Antarctica have reported three morphologically distinct hypolithic community types: cyanobacteria dominated (type I), fungus dominated (type II) and moss dominated (type III). Here we present terminal-restriction fragment length polymorphism analyses to elucidate the bacterial community structure in hypolithons and the surrounding soils. We show clear and robust distinction in bacterial composition between bulk surface soils and hypolithons. Moreover, the bacterial assemblages were similar in types II and III hypolithons and clearly distinct from those found in type I. Through 16S rRNA gene 454 pyrosequencing, we show that Proteobacteria dominated all three types of hypolithic communities. As expected, Cyanobacteria were more abundant in type I hypolithons, whereas Actinobacteria were relatively more abundant in types II and III hypolithons, and were the dominant group in soils. Using a probabilistic dissimilarity metric and random sampling, we demonstrate that deterministic processes are more important in shaping the structure of the bacterial community found in types II and III hypolithons. Most notably, the data presented in this study suggest that hypolithic bacterial communities establish via a successional model, with the type I hypolithons acting as the basal development state.
隐花植物（在半透明岩石底面发育的隐秘微生物组合）是热荒漠和冷荒漠地区 C 和 N 区域预算的重要贡献者。之前在南极洲东部干燥谷的研究报告了三种形态上明显不同的隐花植物群落类型：蓝藻占主导地位（I 型）、真菌占主导地位（II 型）和苔藓占主导地位（III 型）。在这里，我们使用末端限制性片段长度多态性分析来阐明隐花植物和周围土壤中的细菌群落结构。我们表明，在块状表面土壤和隐花植物之间，细菌组成有明显而稳健的区别。此外，II 型和 III 型隐花植物中的细菌组合相似，与 I 型中发现的明显不同。通过 16S rRNA 基因 454 焦磷酸测序，我们表明所有三种类型的隐花植物群落都以变形菌门为主。正如预期的那样，蓝藻在 I 型隐花植物中更为丰富，而放线菌在 II 型和 III 型隐花植物中相对更为丰富，并且是土壤中的主要群体。使用概率不相似性度量和随机抽样，我们证明了确定性过程在塑造 II 型和 III 型隐花植物中细菌群落结构方面更为重要。最值得注意的是，本研究中的数据表明，隐花植物细菌群落通过一个演替模型建立，I 型隐花植物作为基础发育状态。
