Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, calle Profesor Albareda 1, 18008, Granada, Spain.
Sci Rep. 2019 Feb 8;9(1):1695. doi: 10.1038/s41598-018-38123-z.
Melojo oak (Quercus pyrenaica Willd.) is a key tree species of Mediterranean forests; however, these forests show an advanced stage of deterioration in the Iberian Peninsula. Plant-associated microorganisms play an essential role improving their host's fitness, hence, a better understanding of oak rhizospheric microbiome, especially of those active members, could be the first step towards microbiome-based approaches for oak-forest improvement. Here we reported, for the first time, the diversity of total (DNA-based) and potentially active (RNA-based) bacterial communities of different melojo-oak forest formations through pyrosequencing of 16S rRNA gene amplicons. We found that potentially active bacterial communities were as rich and diverse as total bacterial communities, but different in terms of relative abundance patterns in some of the studied areas. Both core microbiomes were dominated by a relatively small percentage of OTUs, most of which showed positive correlation between both libraries. However, the uncoupling between abundance (rDNA) and potential activity (rRNA) for some taxa suggests that the most abundant taxa are not always the most active, and that low-abundance OTUs may have a strong influence on oak's rhizospheric ecology. Thus, measurement of rRNA:rDNA ratio could be helpful in identifying major players for the development of bacterial bioinoculants.
梅洛霍橡树（Quercus pyrenaica Willd.）是地中海森林的关键树种；然而，这些森林在伊比利亚半岛已经处于严重退化的阶段。与植物相关的微生物在提高宿主适应性方面起着至关重要的作用，因此，更好地了解橡树根际微生物组，特别是那些活跃的成员，可能是基于微生物组的方法来改善橡树森林的第一步。在这里，我们首次通过 16S rRNA 基因扩增子的焦磷酸测序，报道了不同梅洛霍橡树森林形成体的总（基于 DNA）和潜在活跃（基于 RNA）细菌群落的多样性。我们发现，潜在活跃的细菌群落与总细菌群落一样丰富多样，但在一些研究区域的相对丰度模式上有所不同。核心微生物组都由相对较少的 OTUs 主导，其中大多数 OTUs 在两个文库之间呈正相关。然而，一些分类群的丰度（rDNA）和潜在活性（rRNA）之间的解耦表明，最丰富的分类群并不总是最活跃的，低丰度的 OTUs 可能对橡树的根际生态学有强烈的影响。因此，rRNA:rDNA 比值的测量可能有助于识别细菌生物接种剂的主要参与者。
