Rolfes Sönke, Longman Jack, Pahnke Katharina, Engelen Bert
Benthic Microbiology, Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl Von Ossietzky Universität Oldenburg, Oldenburg, Germany.
Marine Isotope Geochemistry, Institute for Chemistry and Biology of the Marine Environment (ICBM), School of Mathematics and Science, Carl Von Ossietzky Universität Oldenburg, Oldenburg, Germany.
Front Microbiol. 2025 Mar 12;16:1526969. doi: 10.3389/fmicb.2025.1526969. eCollection 2025.
Much of the marine sedimentary environment is affected by the deposition of tephra, the explosive products of volcanic eruptions. These tephra layers' geochemical and physical properties often differ substantially from those of the surrounding sediment, forming an extreme carbon-lean environment within the anoxic deep biosphere. Despite this, evidence suggests tephra layers harbor diverse and abundant microbial communities. While little is known about the composition of these communities and even less about their life modes, there is evidence indicating that iron (Fe) plays a vital role for these microorganisms. Here, we aim to link differences in the iron content of tephra layers and surrounding sediments with changes within microbial communities. We combined next-generation sequencing of 16S rRNA genes with geochemical analyses of Fe phases preserved in ancient tephra and sediments recovered from the Norwegian Margin during Expedition 396 of the International Ocean Discovery Program (IODP). In these samples, basaltic tephra contained nearly double Fe as surrounding sediments, with the majority hosted in "reducible" Fe(III) oxides, whilst sedimentary Fe is primarily in "easily reducible" Fe(III) oxides. Basaltic tephra harbored distinct microbial communities that differed from the surrounding sediment in composition and predicted metabolic properties. These predictions suggest a higher potential for the assimilatory use of more complex Fe(III) sources in tephra, indicating the microbes are able to exploit the "reducible" Fe(III) found in high quantities in these layers. Our findings confirm the few previous studies that have suggested distinct microbial communities to occur in marine tephra layers. Deciphering the role of iron for indigenous microorganisms hints at how life might flourish in this extreme environment. This has implications for understanding tephra layers as a ubiquitous component of the deep biosphere.
许多海洋沉积环境受到火山灰（火山爆发的爆炸性产物）沉积的影响。这些火山灰层的地球化学和物理性质通常与周围沉积物有很大差异，在缺氧的深部生物圈中形成了一个极端贫碳的环境。尽管如此，有证据表明火山灰层中存在多样且丰富的微生物群落。虽然对这些群落的组成知之甚少，对它们的生活方式更是了解不多，但有证据表明铁（Fe）对这些微生物起着至关重要的作用。在这里，我们旨在将火山灰层和周围沉积物中铁含量的差异与微生物群落的变化联系起来。我们将16S rRNA基因的新一代测序与对国际大洋发现计划（IODP）第396航次从挪威边缘采集的古代火山灰和沉积物中保存的铁相进行的地球化学分析相结合。在这些样本中，玄武质火山灰中的铁含量几乎是周围沉积物的两倍，大部分铁存在于“可还原”的Fe(III)氧化物中，而沉积铁主要存在于“易还原”的Fe(III)氧化物中。玄武质火山灰中含有独特的微生物群落，其组成和预测的代谢特性与周围沉积物不同。这些预测表明，火山灰中更复杂的Fe(III)源被同化利用的潜力更高，这表明微生物能够利用这些层中大量存在的“可还原”Fe(III)。我们的研究结果证实了之前少数几项表明海洋火山灰层中存在独特微生物群落的研究。解读铁对本地微生物的作用，有助于揭示生命在这种极端环境中如何繁荣。这对于理解火山灰层作为深部生物圈中普遍存在的组成部分具有重要意义。
