Moors Hugo, De Craen Mieke, Smolders Carla, Provoost Ann, Leys Natalie
Microbiology Unit, Belgian Nuclear Research Center (SCK CEN), Nuclear Medical Applications Institute (NMA), Mol, Belgium.
Research and Development Disposal, Belgian Nuclear Research Center (SCK CEN), Waste and Disposal (W&D), Mol, Belgium.
Front Microbiol. 2023 Jul 14;14:1134760. doi: 10.3389/fmicb.2023.1134760. eCollection 2023.
Microbes are the Earth life forms that have the highest degree of adaptability to survive, live, or even proliferate in very hostile environments. It is even stated that microbes can cope with any extreme physico-chemical condition and are, therefore, omnipresent all over the Earth: on all the continents, inside its crust and in all its waterbodies. However, our study suggests that there exists areas and even water rich environments on Earth where no life is possible. To support the fact that water rich environments can be lifeless, we performed an extensive survey of 10 different hyper extreme waterbodies of the halo-volcanic Dallol complex (Danakil depression, Ethiopia, Horn of Africa). In our study, we combined physico-chemical analyses, mineralogical investigations, XRD and SEM-EDX analyses, ATP measurements, 16S rDNA microbial community determinations, and microbial culturing techniques. According to our findings, we suggest that the individual physico-chemical parameters, water activity, and kosmo-chaotropicity, are the two most important factors that determine whether an environment is lifeless or capable of hosting specific extreme lifeforms. Besides, waterbodies that contained saturated levels of sodium chloride but at the same time possessed extreme low pH values, appeared to be poly-extreme environments in which no life could be detected. However, we clearly discovered a low diversity microbial community in waterbodies that were fully saturated with sodium chloride and only mildly acidic. Our results can be beneficial to more precisely classify whole or certain areas of planetary bodies, including water rich environments, as either potentially habitable or factual uninhabitable environments.
微生物是地球上适应性最强的生命形式，能够在极其恶劣的环境中生存、繁衍。甚至有人认为，微生物能够应对任何极端的物理化学条件，因此在地球上无处不在：在所有大陆、地壳内部以及所有水体中。然而，我们的研究表明，地球上存在一些区域，甚至是富含水的环境，在这些地方生命无法存在。为了证明富含水的环境可能没有生命，我们对达洛尔火山复合体（位于埃塞俄比亚的达纳吉尔凹地，非洲之角）的10个不同的超极端水体进行了广泛调查。在我们的研究中，我们结合了物理化学分析、矿物学研究、X射线衍射和扫描电子显微镜-能谱分析、三磷酸腺苷测量、16S核糖体DNA微生物群落测定以及微生物培养技术。根据我们的研究结果，我们认为，单独的物理化学参数、水活度和宇宙促溶度是决定一个环境是否没有生命或是否能够容纳特定极端生命形式的两个最重要因素。此外，含有饱和氯化钠水平但同时具有极低pH值的水体似乎是多极端环境，在其中无法检测到生命。然而，我们在完全饱和氯化钠且仅呈弱酸性的水体中清楚地发现了一个低多样性的微生物群落。我们的研究结果有助于更精确地将包括富含水的环境在内的整个或某些行星体区域分类为潜在可居住或实际不可居住的环境。
