Frommlet Jörg C, Sousa Maria L, Alves Artur, Vieira Sandra I, Suggett David J, Serôdio João
Department of Biology, Center for Environmental and Marine Studies (CESAM),
Department of Biology, Center for Environmental and Marine Studies (CESAM).
Proc Natl Acad Sci U S A. 2015 May 12;112(19):6158-63. doi: 10.1073/pnas.1420991112. Epub 2015 Apr 27.
Dinoflagellates of the genus Symbiodinium are commonly recognized as invertebrate endosymbionts that are of central importance for the functioning of coral reef ecosystems. However, the endosymbiotic phase within Symbiodinium life history is inherently tied to a more cryptic free-living (ex hospite) phase that remains largely unexplored. Here we show that free-living Symbiodinium spp. in culture commonly form calcifying bacterial-algal communities that produce aragonitic spherulites and encase the dinoflagellates as endolithic cells. This process is driven by Symbiodinium photosynthesis but occurs only in partnership with bacteria. Our findings not only place dinoflagellates on the map of microbial-algal organomineralization processes but also point toward an endolithic phase in the Symbiodinium life history, a phenomenon that may provide new perspectives on the biology and ecology of Symbiodinium spp. and the evolutionary history of the coral-dinoflagellate symbiosis.
共生藻属的甲藻通常被认为是对珊瑚礁生态系统功能至关重要的无脊椎动物内共生体。然而，共生藻生活史中的内共生阶段本质上与一个更为隐秘的自由生活（体外）阶段相关联，而这个阶段在很大程度上仍未被探索。在这里，我们表明培养中的自由生活的共生藻物种通常会形成钙化的细菌 - 藻类群落，这些群落会产生文石球粒，并将甲藻包裹为石内细胞。这个过程由共生藻的光合作用驱动，但仅在与细菌合作时才会发生。我们的发现不仅将甲藻置于微生物 - 藻类有机矿化过程的版图上，还指向了共生藻生活史中的石内阶段，这一现象可能为共生藻物种的生物学和生态学以及珊瑚 - 甲藻共生关系的进化史提供新的视角。
