Repeatedly Evolved Host-Specific Ectosymbioses between Sulfur-Oxidizing Bacteria and Amphipods Living in a Cave Ecosystem
Repeatedly Evolved Host-Specific Ectosymbioses between Sulfur-Oxidizing Bacteria and Amphipods Living in a Cave Ecosystem
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DOI：
10.1371/journal.pone.0050254
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发表时间：
2012-11-29
期刊：
影响因子：
3.7
通讯作者：
Dattagupta, Sharmishtha
中科院分区：
文献类型：
--
作者：
Bauermeister, Jan;Ramette, Alban;Dattagupta, Sharmishtha
无脊椎动物和硫氧化细菌之间的外共生在含硫海洋环境中广泛存在，并且在多个无脊椎动物门中独立进化。最近在意大利富含硫化物的弗拉萨斯洞穴中报道了淡水栖息地的第一个例子，涉及 Niphargus ictus 片足类和丝状硫丝菌外共生体。随后，在弗拉萨斯内发现了两种新的 Niphargus 物种：N. frasassianus 和 N. montanarius，并被发现与 N. ictus 共存。利用各种显微镜和分子技术，我们发现所有三种生活在弗拉萨西的 Niphargus 物种都含有硫丝菌外共生体，它们属于三个不同的系统发育分支（称为 T1、T2 和 T3）。 T1 和 T3 硫丝菌在弗拉萨斯猪笼草外共生群落中占主导地位，而 T2 和 T3 在强直猪笼草和蒙塔纳里斯猪笼草中普遍存在。三种外共生体的相对分布模式是宿主物种特异性的，并且在不同的采样地点和收集年份中是一致的。 T1-T3 的自由生活对应物在弗拉萨斯洞穴微生物垫中很少或不存在，这表明 Niphargus 之间的外共生传播主要通过种间或种内接种发生。系统发育分析表明 Niphargus-Thiothrix 关联至少独立进化了两次。虽然与 T1 和 T2 的外共生体可能已在 Frasassi 内建立，但 T3 外共生体似乎是由 Niphargus 引入洞穴系统的。
Ectosymbioses between invertebrates and sulfur-oxidizing bacteria are widespread in sulfidic marine environments and have evolved independently in several invertebrate phyla. The first example from a freshwater habitat, involving Niphargus ictus amphipods and filamentous Thiothrix ectosymbionts, was recently reported from the sulfide-rich Frasassi caves in Italy. Subsequently, two new Niphargus species, N. frasassianus and N. montanarius, were discovered within Frasassi and found to co-occur with N. ictus. Using a variety of microscopic and molecular techniques, we found that all three Frasassi-dwelling Niphargus species harbor Thiothrix ectosymbionts, which belong to three distinct phylogenetic clades (named T1, T2, and T3). T1 and T3 Thiothrix dominate the N. frasassianus ectosymbiont community, whereas T2 and T3 are prevalent on N. ictus and N. montanarius. Relative distribution patterns of the three ectosymbionts are host species-specific and consistent over different sampling locations and collection years. Free-living counterparts of T1-T3 are rare or absent in Frasassi cave microbial mats, suggesting that ectosymbiont transmission among Niphargus occurs primarily through inter-or intraspecific inoculations. Phylogenetic analyses indicate that the Niphargus-Thiothrix association has evolved independently at least two times. While ectosymbioses with T1 and T2 may have been established within Frasassi, T3 ectosymbionts seem to have been introduced to the cave system by Niphargus.