Flot Jean-François, Bauermeister Jan, Brad Traian, Hillebrand-Voiculescu Alexandra, Sarbu Serban M, Dattagupta Sharmishtha
Courant Research Center Geobiology, University of Göttingen, Goldschmidtstraße 3, 37077, Göttingen, Germany.
Max Planck Institute for Dynamics and Self-Organization, Biological Physics and Evolutionary Dynamics, Bunsenstraße 10, 37073, Göttingen, Germany.
Mol Ecol. 2014 Mar;23(6):1405-1417. doi: 10.1111/mec.12461. Epub 2013 Sep 14.
Niphargus is a speciose amphipod genus found in groundwater habitats across Europe. Three Niphargus species living in the sulphidic Frasassi caves in Italy harbour sulphur-oxidizing Thiothrix bacterial ectosymbionts. These three species are distantly related, implying that the ability to form ectosymbioses with Thiothrix may be common among Niphargus. Therefore, Niphargus-Thiothrix associations may also be found in sulphidic aquifers other than Frasassi. In this study, we examined this possibility by analysing niphargids of the genera Niphargus and Pontoniphargus collected from the partly sulphidic aquifers of the Southern Dobrogea region of Romania, which are accessible through springs, wells and Movile Cave. Molecular and morphological analyses revealed seven niphargid species in this region. Five of these species occurred occasionally or exclusively in sulphidic locations, whereas the remaining two were restricted to nonsulphidic areas. Thiothrix were detected by PCR on all seven Dobrogean niphargid species and observed using microscopy to be predominantly attached to their hosts' appendages. 16S rRNA gene sequences of the Thiothrix epibionts fell into two main clades, one of which (herein named T4) occurred solely on niphargids collected in sulphidic locations. The other Thiothrix clade was present on niphargids from both sulphidic and nonsulphidic areas and indistinguishable from the T3 ectosymbiont clade previously identified on Frasassi-dwelling Niphargus. Although niphargids from Frasassi and Southern Dobrogea are not closely related, the patterns of their association with Thiothrix are remarkably alike. The finding of similar Niphargus-Thiothrix associations in aquifers located 1200 km apart suggests that they may be widespread in European groundwater ecosystems.
尼氏钩虾属是一个种类丰富的端足类属，在欧洲各地的地下水生境中均有发现。生活在意大利弗拉萨斯硫化洞穴中的三种尼氏钩虾属物种寄生于硫氧化丝状硫细菌外共生体。这三个物种亲缘关系较远，这意味着与丝状硫细菌形成外共生的能力在尼氏钩虾属中可能很常见。因此，在弗拉萨斯以外的硫化含水层中也可能发现尼氏钩虾属与丝状硫细菌的共生关系。在本研究中，我们通过分析从罗马尼亚南多布罗加地区部分硫化含水层收集的尼氏钩虾属和庞氏钩虾属的钩虾，来检验这种可能性，这些含水层可通过泉水、水井和莫维勒洞穴进入。分子和形态学分析揭示了该地区有七种钩虾。其中五种偶尔出现或仅出现在硫化区域，而其余两种则局限于非硫化区域。通过PCR在所有七种多布罗加钩虾物种中检测到丝状硫细菌，并通过显微镜观察到它们主要附着在宿主的附肢上。丝状硫细菌外共生体的16S rRNA基因序列分为两个主要分支，其中一个分支（在此命名为T4）仅出现在从硫化区域收集的钩虾上。另一个丝状硫细菌分支存在于来自硫化和非硫化区域的钩虾上，与先前在弗拉萨斯栖息的尼氏钩虾上鉴定的T3外共生体分支无法区分。尽管来自弗拉萨斯和南多布罗加的钩虾亲缘关系不密切，但它们与丝状硫细菌的共生模式非常相似。在相距1200公里的含水层中发现了类似的尼氏钩虾属与丝状硫细菌的共生关系，这表明它们可能在欧洲地下水生态系统中广泛存在。
