Symbioses between invertebrate animals and chemosynthetic bacteria form the basis of hydrothermal vent ecosystems worldwide. In the Lau Basin, deep-sea vent snails of the genus Alviniconcha associate with either Gammaproteobacteria (A. kojimai, A. strummeri) or Campylobacteria (A. boucheti) that use sulfide and/or hydrogen as energy sources. While the A. boucheti host–symbiont combination (holobiont) dominates at vents with higher concentrations of sulfide and hydrogen, the A. kojimai and A. strummeri holobionts are more abundant at sites with lower concentrations of these reductants. We posit that adaptive differences in symbiont physiology and gene regulation might influence the observed niche partitioning between host taxa. To test this hypothesis, we used high-pressure respirometers to measure symbiont metabolic rates and examine changes in gene expression among holobionts exposed to in situ concentrations of hydrogen (H₂: ~25 µM) or hydrogen sulfide (H₂S: ~120 µM). The campylobacterial symbiont exhibited the lowest rate of H₂S oxidation but the highest rate of H₂ oxidation, with fewer transcriptional changes and less carbon fixation relative to the gammaproteobacterial symbionts under each experimental condition. These data reveal potential physiological adaptations among symbiont types, which may account for the observed net differences in metabolic activity and contribute to the observed niche segregation among holobionts.

无脊椎动物与化学合成细菌之间的共生酶构成了全球热液喷口生态系统的基础。在劳盆地，属的深海通风口蜗牛Alviniconcha关联与任一γ-变形菌（A. kojimai，A. strummeri）或空肠弯曲（A. boucheti）的在使用硫化物和/或氢作为能源。尽管boucheti寄主-共生体组合（holobiont）在排放口中的硫化物和氢气浓度较高，但k.mai曲霉和strummeri在这些还原剂浓度较低的位点，全卤化物含量更高。我们认为，共生体生理和基因调控的适应性差异可能会影响宿主类群之间的生态位分配。为了验证这一假设，我们使用了高压呼吸计来测量共生体代谢率，并检查暴露于原位浓度的氢（H ₂：〜25 µM）或硫化氢（H ₂ S：〜120 µM）的整体生物中基因表达的变化。）。所述campylobacterial共生体表现出最低的速率H的₂小号氧化但H的最高速率₂氧化，以更少的转录变化和固定相对碳少到gammaproteobacterial每个实验条件下的共生体。这些数据揭示了共生体类型之间潜在的生理适应性，这可能解释了观察到的代谢活性的净差异，并有助于观察到的整体生物的利基分离。