Hydrogen consumption by gills of Bathymodiolus spp. collected at the Comfortless cove and Lilliput hydrothermal vent fields in May 2006

The discovery of deep-sea hydrothermal vents in 1977 revolutionized our understanding of the energy sources that fuel primary productivity on Earth. Hydrothermal vent ecosystems are dominated by animals that live in symbiosis with chemosynthetic bacteria. So far, only two energy sources have been shown to power chemosynthetic symbioses: reduced sulphur compounds and methane. Using metagenome sequencing, single-gene fluorescence in situ hybridization, immunohistochemistry, shipboard incubations and in situ mass spectrometry, we show here that the symbionts of the hydrothermal vent mussel Bathymodiolus from the Mid-Atlantic Ridge use hydrogen to power primary production. In addition, we show that the symbionts of Bathymodiolus mussels from Pacific vents have hupL, the key gene for hydrogen oxidation. Furthermore, the symbionts of other vent animals such as the tubeworm Riftia pachyptila and the shrimp Rimicaris exoculata also have hupL. We propose that the ability to use hydrogen as an energy source is widespread in hydrothermal vent symbioses, particularly at sites where hydrogen is abundant.1977年深海热液喷口（deep-sea hydrothermal vents）的发现，彻底革新了学界对地球初级生产力能量来源的认知。热液喷口生态系统的优势类群为与化能合成细菌建立共生关系的动物。截至目前，仅证实两类能量来源可驱动化能合成共生作用：还原态硫化合物与甲烷。本研究借助宏基因组测序（metagenome sequencing）、单基因荧光原位杂交（single-gene fluorescence in situ hybridization）、免疫组织化学（immunohistochemistry）、甲板培养实验（shipboard incubations）以及原位质谱（in situ mass spectrometry）技术，证实大西洋中脊热液喷口巴新贻贝属（Bathymodiolus）贻贝的共生菌可利用氢作为初级生产的能量来源。此外，本研究发现太平洋热液喷口巴新贻贝属贻贝的共生菌携带氢氧化关键基因hupL。进一步检测显示，其他热液喷口动物如管栖蠕虫Riftia pachyptila与虾Rimicaris exoculata的共生菌同样携带hupL。本研究提出，利用氢作为能量来源的能力在热液喷口共生体系中广泛存在，尤其在氢丰度较高的热液喷口位点。