Bourdel Guillaume, Roy-Bolduc Alice, St-Arnaud Marc, Hijri Mohamed
Institut de Recherche en Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, Montréal QC, Canada.
Front Microbiol. 2016 May 12;7:685. doi: 10.3389/fmicb.2016.00685. eCollection 2016.
Plant-root inhabiting fungi are a universal phenomenon found in all ecosystems where plants are able to grow, even in harsh environments. Interactions between fungi and plant roots can vary widely from mutualism to parasitism depending on many parameters. The role of fungal endophytes in phytoremediation of polluted sites, and characterization of the endophytic diversity and community assemblages in contaminated areas remain largely unexplored. In this study, we investigated the composition of endophytic fungal communities in the roots of two plant species growing spontaneously in petroleum-contaminated sedimentation basins of a former petro-chemical plant. The three adjacent basins showed a highly heterogeneous pattern of pollutant concentrations. We combined a culture-based isolation approach with the pyrosequencing of fungal ITS ribosomal DNA. We selected two species, Eleocharis erythropoda Steud. and Populus balsamifera L., and sampled three individuals of each species from each of three adjacent basins, each with a different concentration of petroleum hydrocarbons. We found that contamination level significantly shaped endophytic fungal diversity and community composition in E. erythropoda, with only 9.9% of these fungal Operational Taxonomic Units (OTUs) retrieved in all three basins. However, fungal community structure associated with P. balsamifera remained unaffected by the contamination level with 28.2% of fungal OTUs shared among all three basins. This could be explained by the smaller differences of pollutant concentrations in the soil around our set of P. balsamifera sampless compared to that around our set of E. erythropoda samples. Our culture-based approach allowed isolation of 11 and 30 fungal endophytic species from surface-sterilized roots of E. erythropoda and P. balsamifera, respectively. These isolates were ribotyped using ITS, and all were found in pyrosequensing datasets. Our results demonstrate that extreme levels of pollution reduce fungal diversity and shape community composition in E. erythropoda. Our findings shed light on the effect of soil petroleum contamination on fungal endophytic communities and could help to develop strategies for improving phytoremediation using fungal endophytes.
植物根系定殖真菌是一种普遍存在的现象，在所有植物能够生长的生态系统中都能发现，即使是在恶劣环境中。真菌与植物根系之间的相互作用因许多参数而异，范围从共生到寄生。真菌内生菌在污染场地植物修复中的作用，以及污染区域内生菌多样性和群落组合的特征，在很大程度上仍未得到探索。在本研究中，我们调查了在前石化厂受石油污染的沉积盆地中自然生长的两种植物根系内生真菌群落的组成。三个相邻的盆地呈现出污染物浓度高度异质的模式。我们将基于培养的分离方法与真菌ITS核糖体DNA的焦磷酸测序相结合。我们选择了两种植物，红褐叶荸荠（Eleocharis erythropoda Steud.）和香脂杨（Populus balsamifera L.），并从三个相邻盆地中的每个盆地采集每种植物的三个个体样本，每个盆地的石油烃浓度不同。我们发现，污染水平显著影响了红褐叶荸荠内生真菌的多样性和群落组成，在所有三个盆地中仅检索到这些真菌操作分类单元（OTU）的9.9%。然而，与香脂杨相关的真菌群落结构不受污染水平的影响，所有三个盆地中共有28.2%的真菌OTU。这可以通过我们采集的香脂杨样本周围土壤中污染物浓度的差异小于红褐叶荸荠样本周围土壤中污染物浓度的差异来解释。我们基于培养的方法分别从红褐叶荸荠和香脂杨表面消毒的根系中分离出11种和30种真菌内生菌。使用ITS对这些分离株进行核糖体分型，并且在焦磷酸测序数据集中都能找到。我们的结果表明，极端污染水平会降低红褐叶荸荠中的真菌多样性并塑造群落组成。我们的研究结果揭示了土壤石油污染对真菌内生群落的影响，并有助于制定利用真菌内生菌改善植物修复的策略。
