Liu Cong, Zhang Jian, Li Qiqi, Zhang Yuehuan, Zhang Si, Yu Ziniu, Li Jun, Li Jie
CAS Key Laboratory of Tropical Marine Bio-Resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
ISME Commun. 2025 Mar 2;5(1):ycaf037. doi: 10.1093/ismeco/ycaf037. eCollection 2025 Jan.
Giant clams, with their significant ecological importance, depend on associated bacteria for their health and development, yet the transmission modes and succession of community dynamics of these bacteria remain poorly understood. This study employed 16S rRNA gene sequencing and microscopy to investigate the transmission and community dynamics of symbiotic bacteria in the giant clam during early developmental stages (fertilized eggs, blastocyst, D-larvae, and pediveliger larvae). Fluorescence in situ hybridization and transmission electron microscopy did not detect internal symbiotic bacteria in fertilized eggs and adult gonad gametes, but scanning electron microscopy revealed microbial structures on egg surface microvilli, suggesting their role as microbial carriers. 16S rRNA sequencing confirmed microbial presence in fertilized eggs, indicating bacterial acquisition via external vertical transmission (adherence to microvilli) or horizontal transmission. Given the lack of internalized bacteria in reproductive organs, we prefer to classify the symbiotic bacteria acquisition as horizontal transmission. Microbial community analysis showed that acquired a significant portion of its microbiome from seawater throughout its development. Before reaching the pediveliger stage, the bacterial community composition closely resembled that of the surrounding seawater, primarily featuring the family . As matured, the host's selective pressure increased (e.g. deterministic assembly), which simplified the microbial community and reduced diversity. During the pediveliger stage, the genus became dominant, forming a large proportion of the bacterial community within the gonads. This highlights the ecological significance of host-microbe interactions in maintaining biodiversity and driving ecosystem stability through dynamic community assembly processes.
巨型蛤蜊具有重要的生态意义，其健康和发育依赖于共生细菌，然而这些细菌的传播模式和群落动态演替仍知之甚少。本研究采用16S rRNA基因测序和显微镜技术，调查巨型蛤蜊早期发育阶段（受精卵、囊胚、D形幼虫和壳顶幼虫）共生细菌的传播和群落动态。荧光原位杂交和透射电子显微镜未在受精卵和成年性腺配子中检测到内部共生细菌，但扫描电子显微镜显示卵表面微绒毛上有微生物结构，表明它们作为微生物载体的作用。16S rRNA测序证实受精卵中存在微生物，表明细菌通过外部垂直传播（附着于微绒毛）或水平传播获得。鉴于生殖器官中缺乏内化细菌，我们倾向于将共生细菌的获得归类为水平传播。微生物群落分析表明，其在整个发育过程中从海水中获得了很大一部分微生物组。在达到壳顶幼虫阶段之前，细菌群落组成与周围海水的非常相似，主要以 科为特征。随着其成熟，宿主的选择压力增加（例如确定性组装），这简化了微生物群落并降低了多样性。在壳顶幼虫阶段， 属成为优势属，在性腺内形成了很大比例的细菌群落。这突出了宿主 - 微生物相互作用在通过动态群落组装过程维持生物多样性和推动生态系统稳定性方面的生态意义。
