Data from: A microbiotic survey of lichen-associated bacteria reveals a new lineage from the Rhizobiales

This study uses a set of PCR-based methods to examine the putative microbiota associated with lichen thalli. In initial experiments, generalized oligonucleotide-primers for the 16S rRNA gene resulted in amplicon pools populated almost exclusively with fragments derived from lichen photobionts (i.e., Cyanobacteria or chloroplasts of algae). This effectively masked the presence of other lichen-associated prokaryotes. In order to facilitate the study of the lichen microbiota, 16S ribosomal oligonucleotide-primers were developed to target Bacteria, but exclude sequences derived from chloroplasts and Cyanobacteria. A preliminary microbiotic survey of lichen thalli using these new primers has revealed the identity of several bacterial associates, including representatives of the extremophilic Acidobacteria, bacteria in the families Acetobacteraceae and Brucellaceae, strains belonging to the genus Methylobacterium, and members of an undescribed lineage in the Rhizobiales. This new lineage was investigated and characterized through molecular cloning, and was found to be present in all examined lichens that are associated with green algae. There is evidence to suggest that members of this lineage may both account for a large proportion of the lichen-associated bacterial community and assist in providing the lichen thallus with crucial nutrients such as fixed nitrogen.

本研究采用一系列基于聚合酶链式反应（PCR）的方法，探究与地衣体（lichen thalli）相关的潜在微生物群落。在初始实验中，针对16S核糖体RNA（16S rRNA）基因的通用寡核苷酸引物所扩增得到的扩增子库，几乎完全由地衣光合共生体（即蓝细菌（Cyanobacteria）或藻类叶绿体）来源的片段构成，这实质上掩盖了其他与地衣相关的原核生物的存在。为助力地衣微生物群的研究，我们开发了靶向细菌、但排除叶绿体与蓝细菌来源序列的16S核糖体寡核苷酸引物。利用这些新引物对地衣体进行的初步微生物群落调查，已揭示了数种地衣相关细菌的分类学身份，包括嗜极端环境的酸杆菌门（Acidobacteria）代表类群、醋杆菌科（Acetobacteraceae）与布鲁氏菌科（Brucellaceae）的细菌、甲基杆菌属（Methylobacterium）菌株，以及根瘤菌目（Rhizobiales）中一类尚未被描述的演化支成员。我们通过分子克隆对这一新演化支开展研究与表征，发现其普遍存在于所有检测过的与绿藻共生的地衣中。有证据表明，该演化支的类群不仅可占地衣相关细菌群落的较大比例，还可协助地衣体获取固定态氮等关键营养物质。