Vohník M, Burdíková Z, Albrechtová J, Vosátka M
Department of Mycorrhizal Symbioses, Institute of Botany, Academy of Sciences of the Czech Republic (ASCR), Lesní 323, Průhonice, 252 43, Czech Republic.
Microb Ecol. 2009 Jan;57(1):203-14. doi: 10.1007/s00248-008-9402-y. Epub 2008 Jul 8.
Common occurrence of testate amoebae (TA) in the rhizosphere of mycorrhizal plants indicates existence of yet undocumented ecological interactions, involving three distinct groups of organisms: soil protists, mycorrhizal fungi, and their host plants. This tripartite relationship was to date investigated only to a limited extent, despite its probable importance for processes taking place in the mycorrhizosphere. In this study, we (1) explored spectra of different TA genera naturally associated with the rhizoplane of three autochthonous European Rhododendron species, (2) screened natural fungal colonization of the TA shells occupying the rhizoplane of selected rhododendrons, and (3) carried out two in vitro experiments addressing the question whether TA shells may serve as a nutrient source for ericoid mycorrhizal fungi (ErMF) and dark septate endophytes (DSE). Our field observations indicated that TA regularly associated with the rhizoplane of all screened rhododendrons and that ErMF and/or DSE associated with their roots possibly exploited the TA shells as a nutrient source. We were unable to detect any major differences among the TA spectra from the rhizoplanes with respect to the three Rhododendron species. The spectra were dominated by Diplochlamys, Centropyxis, Cyclopyxis, Euglypha, Trinema, and Assulina. Positive, neutral, and negative associations were found for various TA genera x Rhododendron species combinations. The highest fungal colonization was observed in Centropyxidae and Trigonopyxidae, reaching up to 45% of the shells in the case of Trigonopyxis. In the in vitro experiments, both ErMF Rhizoscyphus ericae and DSE Phialocephala fortinii regularly colonized TA shells, utilizing them as a source of nutrients. We hypothesize a complex relationship between ErMF-DSE and TA. If corroborated, it would represent an interesting nutrient loop in the mycorrhizosphere of ericaceous plants.
在菌根植物根际中经常出现有壳变形虫（TA），这表明存在尚未被记录的生态相互作用，涉及三类不同的生物体：土壤原生生物、菌根真菌及其寄主植物。尽管这种三方关系可能对菌根根际中发生的过程很重要，但迄今为止对其研究还很有限。在本研究中，我们（1）探索了与三种欧洲本土杜鹃花属植物根表自然相关的不同TA属的谱图，（2）筛选了占据所选杜鹃花根表的TA壳上的自然真菌定殖情况，（3）进行了两项体外实验，以解决TA壳是否可作为石楠类菌根真菌（ErMF）和深色有隔内生菌（DSE）的营养源这一问题。我们的实地观察表明，TA经常与所有筛选的杜鹃花根表相关联，并且与它们根系相关的ErMF和/或DSE可能将TA壳作为营养源。我们未能检测到三种杜鹃花属植物根表TA谱图之间的任何主要差异。这些谱图以双壳虫属、砂壳虫属、圆壳虫属、真壳虫属、三肋虫属和类砂壳虫属为主。对于各种TA属×杜鹃花属植物组合，发现了正、中性和负相关关系。在砂壳虫科和三角砂壳虫科中观察到最高的真菌定殖率，在三角砂壳虫的情况下，高达壳的45%。在体外实验中，ErMF欧石楠类菌根菌和DSE福尔蒂瓶霉都经常定殖在TA壳上，并将其作为营养源利用。我们推测ErMF-DSE和TA之间存在复杂的关系。如果得到证实，这将代表石楠类植物菌根根际中一个有趣的营养循环。
