Influence of fluids from the ocean crust on growth and activity of deep-biosphere populations (IODP Leg 301)

Juan de Fuca Ridge东侧IODP Site 1301沉积物柱（水深2650 m，沉积物覆盖面积265 m）的特征是海底地壳的热液扩散流动，温度梯度为0.23°C/m，有两个硫化氢-甲烷过渡带。我们项目的一个目标是通过向深埋的沉积物中引入电子受体来了解流体作为海洋深层生物圈驱动力的作用。这一假设得到了沿沉积物柱的细胞量化和活性测量的支持。沉积物-基底界面上细胞数量的增加首次为地壳流体刺激下的微生物群落提供了证据。潜在的磷酸酶活性在沉积物-基底界面的缺磷层中增强。在较低的硫酸盐-甲烷过渡区内，硫酸盐还原速率和甲烷厌氧氧化速率升高。进一步的研究集中在分离和鉴定本地微生物。分子筛选用于确定来自所有沉积层的富集培养物的微生物组成，揭示了不同的种型。然而，由于我们处理的是生长缓慢的原核生物，它们需要长达六个月的时间来形成一个菌落。因此，新分离物的分离和鉴定以及出版物的准备工作将在申请期结束前完成。

The sediment column of IODP Site 1301 of the eastern flank of the Juan de Fuca Ridge (water depth: 2650 m, sediment coverage: 265 m) is characterised by a diffusive flow of hydrothermal fluids from the underlying ocean crust, a steep temperature gradient of 0.23 °C/m and two sulfate-methane transition zones. One goal of our project is to understand the role of fluids as a driving force for the marine deep biosphere by introducing electron acceptors to deeply buried sediments. This hypothesis was supported by cell quantification and activity measurements along the sediment column. Elevated cell numbers at the sediment-basement interface gave the first evidence for a microbial community stimulated by crustal fluids. Potential phosphatase activity was enhanced in phosphate-depleted layers towards the sediment-basement interface. Rates of sulfate reduction and anaerobic oxidation of methane were elevated within the lower sulfate-methane transition zone. Further investigations are focussed on isolation and characterisation of indigenous microorganisms. Molecular screening, used to determine the microbial composition of enrichment cultures from all sediment layers, revealed different phylotypes. However, as we are dealing with slowly growing prokaryotes, they need up to six months to form a colony. Therefore, the isolation and characterisation of new isolates and the preparation of publications will be finished until the end of the application period.