Bernardini Simone, Abbassi Anas, Cipollari Paola, Ventura Giancarlo Della, Saiz-Jimenez Cesareo, Mugnaioli Enrico, Jovane Luigi, Sodo Armida, Bellatreccia Fabio, Zaghloul Mohamed N, Cosentino Domenico
Dipartimento di Scienze, Università di Roma Tre, Roma, Italy.
Fachbereich Erdsystemwissenschaften, Universität Hamburg, Hamburg, Germany.
Geobiology. 2025 Sep-Oct;23(5):e70031. doi: 10.1111/gbi.70031.
Large-scale geological processes shape microbial habitats and drive the evolution of life on Earth. During the Oligocene, convergence between Africa and Europe led to the opening of the Western Mediterranean Basin, a deep-ocean system characterized by fluid venting, oxygen depletion, and the absence of benthic fauna. In this extreme, inhospitable seafloor environment, fusiform objects known as Tubotomaculum formed, whose origin has long remained controversial. We show that these enigmatic mineralizations consist of nanosized, poorly crystalline, phosphorus-rich Mn-Fe compounds produced through microbial mediation. They preserve carbonaceous material together with morphological, chemical, and mineralogical biosignatures, including high Mn oxidation state (3.9 ± 0.15), cell envelopes, extracellular polymeric substances (EPS), cell-EPS partitioning of redox-sensitive Mn and Fe, cluster-assembled microbial cells, microbialite-like and branching structures, and channel networks for nutrient transport. Geochemical signatures indicate precipitation under suboxic to anoxic, non-sulfidic (post-oxic) conditions from mixed seawater-hydrothermal fluids, with exposure on the seafloor prior to burial. The fusiform architecture of these self-organized microbial populations suggests shaping by nutrient-rich bottom currents associated with venting activity. This study provides a detailed glimpse into initial benthic colonization of the nascent Western Mediterranean Basin and establishes Tubotomaculum as a model for investigating biomineralization and microbial adaptation in extreme environments, with implications for the search for life beyond Earth.
大规模地质过程塑造了微生物栖息地，并推动了地球上生命的演化。在渐新世期间，非洲与欧洲的碰撞导致了西地中海盆地的形成，这是一个以流体排放、缺氧以及缺乏底栖动物为特征的深海系统。在这种极端恶劣、不适宜居住的海底环境中，形成了一种被称为管形矿囊的梭形物体，其起源长期以来一直存在争议。我们发现，这些神秘的矿化结构由通过微生物介导产生的纳米级、结晶度差、富含磷的锰铁化合物组成。它们保存了含碳物质以及形态、化学和矿物学的生物特征，包括高氧化态的锰（3.9±0.15）、细胞膜、胞外聚合物（EPS）、氧化还原敏感的锰和铁在细胞与EPS之间的分配、簇状聚集的微生物细胞、类微生物岩和分支结构以及用于营养物质运输的通道网络。地球化学特征表明，这些物质是在缺氧至无氧、非硫化（氧化后）条件下，由混合的海水 - 热液流体沉淀形成的，在埋藏之前曾暴露于海底。这些自组织微生物群体的梭形结构表明，它们是由与排放活动相关的富含营养的底层水流塑造而成的。这项研究详细展示了新生的西地中海盆地最初的底栖生物定殖情况，并将管形矿囊确立为研究极端环境中生物矿化和微生物适应性的模型，对寻找地外生命具有启示意义。
