中国の南北水移送プロジェクトで優占する珪藻、細菌との共生によって優位性を維持（Dominant Diatom Thrives via Partnership with Bacteria in China’s Major Water Project）

2026-09-08 中国科学院（CAS）

Two diatom species from the Middle Route of China’s South‑to‑North Water Diversion Project: C. atomus, a long‑term dominant species, and U. ulna, a short‑term dominant species. (Image by IHB)

＜関連情報＞

• https://english.cas.cn/newsroom/research-news/202609/t20260908_1192772.shtml
• https://academic.oup.com/ismecommun/article/6/1/ycag211/8740006?login=false

藻類圏の微生物叢は珪藻の生態的優位性に寄与する： Cyclotella atomusとUlnaria ulna の比較研究 Phycosphere microbiome contributes to ecological dominance of diatoms: a comparative study of Cyclotella atomus and Ulnaria ulna

Gaofei Song,Fengfeng Cheng,Zhixian Qiao,Feng Ge,Yonghong Bi
ISME Communications  Published:23 July 2026
DOI:https://doi.org/10.1093/ismeco/ycag211

Abstract

Diatoms play a crucial role in aquatic ecosystems, yet the mechanisms underlying their long-term dominance remain poorly understood. This study investigated the relationship between diatom ecological persistence and their phycosphere bacterial communities by comparing the long-term dominant species Cyclotella atomus with the short-term dominant species Ulnaria ulna. 16S rRNA gene sequencing combined with predictive functional profiling revealed that the bacterial community associated with C. atomus was more diverse, stable, and interconnected than that associated with U. ulna. Taxonomic analysis identified key bacterial taxa such as Gemmatimonas, Sphingobium, and Pseudorhodoferax enriched in C. atomus. Co-occurrence network analysis demonstrated higher microbial interaction complexity in C. atomus, enhancing functional redundancy and ecosystem stability. Functional predictions indicated significant enrichment in carbohydrate metabolism (glycosaminoglycan degradation, pentose/glucose interconversion) and stress response pathways (betaine biosynthesis, xenobiotic metabolism by cytochrome P450) in the C. atomus microbiome, supporting a mutualistic relationship in which diatom-derived extracellular polymeric substances sustains specialized bacteria that reciprocate with vitamin B₁₂, phytohormones, and chemical defenses. Based on these results, a mutually reinforced symbiotic cycle model was proposed to illustrate how the diatom and its phycosphere microbiome established a resilient holobiont capable of prolonged ecological dominance. The bacterial community associated with each diatom species exhibited host specificity and contributed to the maintenance of host dominance. These findings highlight the critical role of microbial partnerships in diatom success, offering new insights for predicting phytoplankton community dynamics and managing aquatic ecosystems.