Metagenomic analysis exploring soil microbial communities associated with Antarctic vascular plants. rhizospheric metagenomes

The Antarctic ecosystem is one of the most stressful natural habitats, especially for terrestrial plants. Likewise, only two vascular plants have colonized the Antarctic environment, Colobanthus quitensis (Caryophyllaceae) and Deschampsia antaractica (Poaceae). Although both plants colonize Antarctica, C. quitensis is mainly found growing in association with D. antarctica in more stressful areas, while D. antarctica is capable to grow alone in areas with higher abiotic stress. Positive inter-specific interactions play a pivotal role in the structure and functioning of several ecosystems in harsh environments, and possibly they play a role in Antarctic terrestrial ecosystems.In this study, we compare the rhizosphere microbiomes associated with Colobanthus quitensis, either growing alone or associated with Deschampsia antarctica, using shotgun metagenomic DNA sequencing technology for comparative metagenomics. This approach allows us to gain insight into the rhizospheric microbial community structure associated with C. quitensis and C. quitensis – D. antarctica, through the study of soil’s microbial taxonomic diversity, including non-culturable organisms. Such analysis could also provide valuable information regarding microbial functional diversity. This functional diversity might be playing important roles in conferring different degrees of tolerance to Antarctica’s harsh environmental conditions such as low temperatures, desiccation, and low water and nutrient availability, which could help to explain the “enigma” of the success of these plant species in such harsh environments.

南极生态系统是全球压力最为严苛的自然生境之一，对陆生植物而言尤甚。目前仅有两种维管植物成功定植南极环境，分别为南极漆姑草（Colobanthus quitensis，石竹科Caryophyllaceae）与南极发草（Deschampsia antarctica，禾本科Poaceae）。尽管二者均可在南极定植，但南极漆姑草（C. quitensis）多与南极发草伴生于胁迫程度更高的区域，而南极发草（D. antarctica）则可单独在非生物胁迫更强的生境中生长。种间正相互作用（positive inter-specific interactions）在极端环境下多个生态系统的结构与功能中发挥关键调控作用，其亦可能在南极陆地生态系统中扮演重要角色。
本研究采用鸟枪宏基因组DNA测序（shotgun metagenomic DNA sequencing）技术开展比较宏基因组学（comparative metagenomics）分析，对比单独生长的南极漆姑草，以及与南极发草伴生的南极漆姑草的根际微生物组（rhizosphere microbiomes）。该方法可通过探究土壤微生物分类多样性（涵盖不可培养微生物），解析与南极漆姑草单生、南极漆姑草与南极发草伴生相关的根际微生物群落结构。此类分析还可提供关于微生物功能多样性的宝贵信息。这类功能多样性或许在赋予植物适应南极极端环境（如低温、干旱、水分与养分匮乏）的不同耐受程度中发挥重要作用，或有助于解释这两种植物何以能在如此严苛的环境中成功存活这一“谜团”。