Malas Judy, Russo Daniel C, Bollengier Olivier, Malaska Michael J, Lopes Rosaly M C, Kenig Fabien, Meyer-Dombard D'Arcy R
Department of Earth and Environmental Sciences, University of Illinois Chicago, Chicago, IL, United States.
Nantes Université, Univ Angers, Le Mans Université, CNRS, Laboratoire de Planétologie et Géosciences, LPG UMR 6112, Nantes, France.
Front Microbiol. 2024 Feb 13;15:1293928. doi: 10.3389/fmicb.2024.1293928. eCollection 2024.
High hydrostatic pressure (HHP) is a key driver of life's evolution and diversification on Earth. Icy moons such as Titan, Europa, and Enceladus harbor potentially habitable high-pressure environments within their subsurface oceans. Titan, in particular, is modeled to have subsurface ocean pressures ≥ 150 MPa, which are above the highest pressures known to support life on Earth in natural ecosystems. Piezophiles are organisms that grow optimally at pressures higher than atmospheric (0.1 MPa) pressure and have specialized adaptations to the physical constraints of high-pressure environments - up to ~110 MPa at Challenger Deep, the highest pressure deep-sea habitat explored. While non-piezophilic microorganisms have been shown to survive short exposures at Titan relevant pressures, the mechanisms of their survival under such conditions remain largely unelucidated. To better understand these mechanisms, we have conducted a study of gene expression for MR-1 using a high-pressure experimental culturing system. MR-1 was subjected to short-term (15 min) and long-term (2 h) HHP of 158 MPa, a value consistent with pressures expected near the top of Titan's subsurface ocean. We show that MR-1 is metabolically active at HHP and is capable of viable growth following 2 h exposure to 158 MPa, with minimal pressure training beforehand. We further find that MR-1 regulates 264 genes in response to short-term HHP, the majority of which are upregulated. Adaptations include upregulation of the genes , and involved in arginine biosynthesis and regulation of genes involved in membrane reconfiguration. MR-1 also utilizes stress response adaptations common to other environmental extremes such as genes encoding for the cold-shock protein CspG and antioxidant defense related genes. This study suggests Titan's ocean pressures may not limit life, as microorganisms could employ adaptations akin to those demonstrated by terrestrial organisms.
高静水压力（HHP）是地球上生命进化和多样化的关键驱动力。土卫六、木卫二和土卫二等冰卫星在其地下海洋中蕴藏着潜在的宜居高压环境。特别是土卫六，据模拟其地下海洋压力≥150兆帕，高于已知自然生态系统中地球上支持生命的最高压力。嗜压菌是在高于大气压力（0.1兆帕）的压力下生长最佳的生物，并且对高压环境的物理限制具有特殊适应性——在已探索的最深海栖息地挑战者深渊可达约110兆帕。虽然已证明非嗜压微生物能在与土卫六相关的压力下短时间存活，但它们在这种条件下的存活机制仍 largely未阐明。为了更好地理解这些机制，我们使用高压实验培养系统对MR - 1进行了基因表达研究。MR - 1经受了158兆帕的短期（15分钟）和长期（2小时）高静水压力，该值与土卫六地下海洋顶部附近预期的压力一致。我们表明，MR - 1在高静水压力下具有代谢活性，并且在预先进行最少压力训练后，暴露于158兆帕2小时后能够存活生长。我们进一步发现，MR - 1响应短期高静水压力调节264个基因，其中大多数基因上调。适应性包括上调参与精氨酸生物合成的基因以及参与膜重构的基因。MR - 1还利用了与其他极端环境共有的应激反应适应性，例如编码冷休克蛋白CspG的基因和与抗氧化防御相关的基因。这项研究表明，土卫六的海洋压力可能不会限制生命，因为微生物可以采用类似于陆地生物所展示的适应性。
