MAC-EXP: Development of a pressurised sampling, experimentation and cultivation system for deep-sea sediments

大多数深海生物生活在高压下的“压电层”（水深超过1 000米或压力超过10兆帕的深海体积）中，依靠从表面沃茨下沉的有机颗粒为食。迄今为止，海洋沉积物中最丰富的生物是原核生物（细菌和古生菌），细菌和古生菌的生物量如此之大，以至于它们被认为是有机物再矿化的主要媒介，这一过程将营养物质释放回水体，因此对海洋生产力和渔业等非常重要。但我们对深海原核生物多样性和生态系统功能的了解却很少。随着渔业、采矿、石油和天然气勘探越来越多地在更深的沃茨水域进行，我们迫切需要提高对深海生态系统功能的了解，以便适当评估此类活动和影响的社会和经济影响，并确保为子孙后代充分管理深海生物多样性和自然资源。不幸的是，这并不容易：我们对深海生物多样性和生态系统功能的了解有限，主要原因在于无法进入深海生物多样性和深海生物地球化学过程对减压的敏感性。压力对例如细菌生理学或生长速率以及微生物进行的许多生物地球化学过程具有显著影响。因此，必须在原地压力下进行有意义的实验，这造成了重大的财政和技术限制。遥控潜水器使我们能够在深海海底进行实验性研究，但尽管现在已经成为可能，但这仍然非常危险和资源密集，需要由大型船只上的大型船员操作的复杂深海遥控潜水器（例如，11名技术人员陪同部署法国深海探测器VICTOR 6000;并且需要大型研究船来容纳和部署它），并且迄今为止很少有这样的系统可用。此外，在大多数情况下，样品在取回时会减压，从而阻止进一步的实验。由于许多深海微生物可能只能在没有减压的情况下培养，这可以解释为什么目前只有不到1%的深海原核生物在培养中。在这里，我们建议开发一个灵活的，具有成本效益的替代原位实验：压力取芯，实验和培养系统，使研究深海原核生物多样性和活动，生态系统的功能，在环境或操纵压力，温度和氧气条件下，从任何中型远洋研究船取芯能力。此外，从取样到培养的持续高压条件克服了与降压有关的现场实验的局限性，这一多重高压釜取芯和实验系统将提供系统测试环境参数，如压力、氧气供应或pH值对深海生物及其生物化学的影响的可能性，以及地球化学和地质微生物过程的速率和途径。该系统还将使海洋生物发现领域的开拓性工作成为可能：海洋微生物的次级代谢产物是化学多样性的丰富来源，若干海洋微生物衍生化合物目前正在进行临床试验。最近的证据表明，深海沉积物中适应压力的细菌产生具有生物活性和不寻常的次级代谢产物。但是，还没有研究过压力适应细菌的次级代谢产物，拟议的加压采样系统提供了进行此类研究的可能性。

Most deep-sea organisms live under high pressure in the "piezosphere" (the volume of the deep-sea at > 1000 m of water depth or > 10MPa pressure) and depend on organic particles sinking down from the surface waters for food. The most abundant organisms by far in marine sediments are prokaryotes (bacteria and archaea), and the biomass of the bacteria and archaea is so great that they are thought to be the main agents of the remineralisation of organic matter, a process which releases nutrients back into the water column and is thus very important for ocean productivity and, for example, fisheries. But our knowledge of deep-sea prokaryote diversity and ecosystem function is scarce. With fishing, mining, oil and gas exploration increasingly taking place in deeper waters, we urgently need to improve our understanding of the functioning of deep-sea ecosystems in order to assess appropriately the societal and economic implications of such activities and impacts and to ensure adequate management of deep-sea biodiversity and natural resources for future generations.Unfortunately, this is not easy: the main reasons for our limited knowledge of deep-sea biodiversity and ecosystem functioning lies in the combination of its inaccessibility with the sensitivity to depressurization of deep-sea organisms and deep-sea biogeochemical processes. Pressure has significant effects on, for example, bacterial physiology or growth rates, as well as many biogeochemical processes that microorganisms conduct. In consequence, meaningful experimentation has to be carried out under in situ pressure, which results in major financial and technical constraints. Remotely Operated Vehicles allow us to conduct experimental research at the deep-sea floor, but although now possible, this is still very risky and resource-intensive, requiring sophisticated deep-sea ROVs, operated by large crews from large vessels (e.g. 11 technical staff accompany a deployment of the French deep-sea ROV VICTOR 6000; and a large research ship is needed to accommodate and deploy it), and to-date very few such systems are available. In addition, samples in most cases suffer depressurization upon retrieval, preventing further experimentation. As many deep-sea microorgansims may only be culturable without depressurization, this may explain why less than 1 % of deep-sea prokaryotes are currently in culture. Here we propose to develop a flexible, cost-effective alternative to in situ experimentation: a pressure-coring, experimentation and cultivation system that enables studies of deep-sea prokaryote biodiversity and activity, and ecosystem functioning, under ambient or manipulated pressure, temperature and oxygen conditions from any medium sized ocean going research ship with coring capability. In addition, the constant high-pressure conditions from sampling to culture overcomes limitations of in situ experiments related to depressurisation.This Multiple-Autoclave-Coring and Experimentation system (MAC-EXP) will provide the possibility to systematically test the influence of environmental parameters, such as pressure, oxygen availability or pH on deep-sea organisms and their biochemistry, as well as on rates and pathways of biogeochemical and geomicrobial processes. The system will also allow pioneering work in the field of marine biodiscovery: secondary metabolites from marine microorganisms are a rich source of chemical diversity and several marine-microbe derived compounds are now in clinical trials. Recent evidence shows that pressure-adapted bacteria from deep-sea sediments produce biologically active and unusual secondary metabolites. But no pressure-adapted bacterial species have ever been investigated for their secondary metabolites and the proposed pressurised sampling system provides the possibility to conduct such studies.