Physical contact and carbon transfer between a lichen-forming Trebouxia alga and a novel Alphaproteobacterium
Physical contact and carbon transfer between a lichen-forming Trebouxia alga and a novel Alphaproteobacterium
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DOI：
10.1099/mic.0.000461
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发表时间：
2017-05-01
期刊：
影响因子：
2.8
通讯作者：
Terai, Yohey
中科院分区：
文献类型：
--
作者：
Kono, Mieko;Tanabe, Hideyuki;Terai, Yohey
分子生物学技术的最新进展已经开始改变地衣作为真菌和光合作用伙伴（绿色藻类和/或蓝细菌）组成的共生生物体的传统认识。各种生物，特别是各种非光合细菌，现在被认为是地衣共生的组成部分。虽然地衣相关的细菌被推断为具有支持共生的功能，但对它们与真菌和藻类的物理和营养相互作用知之甚少。在本研究中，我们确定了地衣形成的真菌和一种新的细菌之间的特定相互作用。从一种地衣松萝（Usneahakonensis）中分离出一株长约8年的松萝（Trebouxia hakonensis）。虽然在该培养物中没有观察到可见的细菌菌落，但从培养物中分离的DNA的高通量测序显示该菌株由Trebouxia菌和Alphaproteobacterium属物种组成。原位杂交结果表明，细菌细胞定位于藻细胞表面。生理分析表明，该细菌能够利用核糖醇，葡萄糖和甘露醇，所有这些都是已知的丰富存在于地衣中。它对三种抗生素都有抗药性。在地衣标本中也发现了与该种密切相关的细菌，表明美国的地衣中也含有该种细菌。hakonensis可能通常与这组细菌有关。新细菌的这些特征表明它可能参与了铀的碳循环。hakonensis作为地衣共生体的一员，在从地衣中分离出来后，不太可能与地衣共生。
Recent progress in molecular techniques has begun to alter traditional recognition of lichens as symbiotic organisms comprised of a fungus and photosynthetic partners (green algae and/or cyanobacteria). Diverse organisms, especially various non-photosynthetic bacteria, are now indicated to be integral components of lichen symbiosis. Although lichen-associated bacteria are inferred to have functions that could support the symbiosis, little is known about their physical and nutritional interaction with fungi and algae. In the present study, we identified specific interaction between a lichen-forming alga and a novel bacterium. Trebouxia alga was isolated from a lichen, Usnea hakonensis, and kept as a strain for 8 years. Although no visible bacterial colonies were observed in this culture, high-throughput sequencing of DNA isolated from the culture revealed that the strain is composed of a Trebouxia alga and an Alphaproteobacterium species. In situ hybridization showed that bacterial cells were localized on the surface of the algal cells. Physiological assays revealed that the bacterium was able to use ribitol, glucose and mannitol, all of which are known to exist abundantly in lichens. It was resistant to three antibiotics. Bacteria closely related to this species were also identified in lichen specimens, indicating that U. hakonensis may commonly associate with this group of bacteria. These features of the novel bacterium suggest that it may be involved in carbon cycling of U. hakonensis as a member of lichen symbiosis and less likely to have become associated with the alga after isolation from a lichen.