University of Vienna, Centre for Microbiology and Environmental Systems Science, Division of Microbial Ecology, Djerassiplatz 1, 1030 Vienna, Austria.
Doctoral School in Microbiology and Environmental Science, University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria.
ISME J. 2024 Jan 8;18(1). doi: 10.1093/ismejo/wrae200.
Like many marine invertebrates, marine lucinid clams have an intimate relationship with beneficial sulfur-oxidizing bacteria located within specialized gill cells known as bacteriocytes. Most previous research has focused on the symbionts in the gills of these (and other) symbiotic bivalves, often assuming that the symbionts only persistently colonize the gills, at least in the adult stage. We used 16S rRNA gene sequencing and digital polymerase chain reaction with symbiont-specific primers targeting the soxB gene on the foot, mantle, visceral mass, and gills of the lucinid clam Loripes orbiculatus. We also used fluorescence in situ hybridization with symbiont-specific probes to examine symbiont distribution at the level of the whole holobiont. Despite 40 years of research on these symbioses, we detected previously unknown populations of symbiont cells in several organs, including the digestive tract. As in the well-studied gills, symbionts in the digestive tract may be housed within host cells. A 14-month starvation experiment without hydrogen sulfide to power symbiont metabolism caused a larger reduction in symbiont numbers in the gills compared to the visceral mass, raising the possibility that symbionts in the digestive tract are persistent and may have a distinct physiology and role in the symbiosis compared with the gill symbionts. Our results highlight the unexpectedly complex relationships between marine lucinid clams and their symbionts and challenge the view that chemosynthetic symbionts are restricted to the gills of these hosts.
与许多海洋无脊椎动物一样，海洋硫贻贝与位于特殊鳃细胞（称为菌胞）内的有益硫氧化细菌有着密切的关系。大多数先前的研究都集中在这些（和其他）共生双壳类动物鳃中的共生体上，通常假设共生体仅持久地定植在鳃中，至少在成体阶段是这样。我们使用 16S rRNA 基因测序和针对 soxB 基因的带有共生体特异性引物的数字聚合酶链反应，对硫贻贝 Loripes orbiculatus 的足部、套膜、内脏团和鳃进行了研究。我们还使用带有共生体特异性探针的荧光原位杂交技术，检查了整个生物整体的共生体分布。尽管对这些共生体进行了 40 年的研究，但我们在包括消化道在内的几个器官中检测到了以前未知的共生体细胞群。与在研究充分的鳃中一样，消化道中的共生体可能位于宿主细胞内。一项为期 14 个月的没有硫化氢为共生体代谢提供动力的饥饿实验导致鳃中共生体数量的减少明显大于内脏团，这表明消化道中的共生体是持久存在的，并且与鳃共生体相比，它们可能具有独特的生理学和在共生关系中的作用。我们的研究结果突出了海洋硫贻贝与其共生体之间出人意料的复杂关系，并挑战了化能合成共生体仅限于这些宿主鳃的观点。
