The role of microbes and biofilms in leaf fossilization

微生物和生物膜在叶子石化中的作用

• 批准号: 465275390
• 负责人: Professorin Dr. Gabriele Bierbaum
• 金额: --
• 依托单位: Institut für Geologische Wissenschaften
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/465275390?language=en
• 关键词: role; microbes; biofilms; leaf; fossilization

Fossils are formed through a complex series of biological, chemical, and geological processes. Plant parts such as leaves are commonly carbonized, or in the case of wood, silicified. In studies on animal carcasses, it has been shown that biofilms produced by bacteria can play a role in the fossilization of soft tissues. Through biofilms, soft-tissue structures can be preserved in exact detail. The negatively charged surface of a biofilm facilitates the precipitation of minerals in the biofilm. In the first funding period, Project B3 investigated the taphonomy of arthropods with a focus on crayfish. Precipitation of calcium carbonate in the crayfish can occur after only two days. Microbiome analysis documented that colonization of the crayfish consisted of a succession of bacterial populations with continuously decreasing oxygen demand. Dominant were bacterial genera that are aggressive producers of proteases, chitinases, and lipases. At higher temperatures, they led to the rapid decay of the crayfish, even in the absence of oxygen; at lower temperatures, the rate of the process was strongly reduced. In contrast to biofilms in animals, the role of microbial biofilms in the genesis of fossil leaf compressions is poorly known. It has been shown in only a few studies that leaf biofilms can form and also incorporate minerals. A mineralized biofilm may have a protective function against herbivores and mechanical damage. Within the framework of Research Unit 2685, the formation of such biofilms in natural settings and in aquaria will be studied in Project C3. In Project C4, the complex processes behind biofilm formation will be elucidated, including which conditions and which bacteria or fungi can lead to mineral precipitation or to the degradation of leaf tissues. To this end, individual strains of bacterial and fungal species will be isolated from the biofilms. Together or alone, these microbes will be incubated with leaves under sterile laboratory conditions, and their influence on the leaf preservation or decay will be analyzed. As soon as a biofilm has been formed, it will be tested which ion concentrations or which metabolic processes (release of phosphate, breakdown of urea, oxidation of iron) are carried out by the bacteria as a prerequisite for the precipitation of minerals on the leaves. Our results from the first funding period have also shown that the decay activity of microorganisms must be stopped or slowed down so that fossilization can continue. This may happen after deposition in sediment, presumably through the release of heavy metals from the acid produced by bacteria in anoxic conditions. For this reason, the effect of heavy metals on biofilms will be investigated in the laboratory to develop a mechanistic model of an early phase of leaf fossilization.

化石是通过一系列复杂的生物、化学和地质过程形成的。植物的某些部分，如叶子，通常被硅化，或者在木材的情况下，被硅化。在对动物尸体的研究中，已经表明细菌产生的生物膜可以在软组织的生物化中发挥作用。通过生物膜，软组织结构可以被精确地保留下来。生物膜的带负电荷的表面促进生物膜中矿物质的沉淀。在第一个供资期，项目B3调查了节肢动物的埋藏学，重点是小龙虾。小龙虾中的碳酸钙沉淀可以在两天后发生。微生物组分析证明，小龙虾的定植由一系列需氧量不断降低的细菌种群组成。占主导地位的是细菌属，它们是蛋白酶、几丁质酶和脂肪酶的积极生产者。在较高的温度下，它们导致小龙虾迅速腐烂，即使在没有氧气的情况下;在较低的温度下，这个过程的速度大大降低。与动物体内的生物膜相比，微生物生物膜在化石叶压缩形成中的作用知之甚少。只有少数研究表明，叶片生物膜可以形成，并含有矿物质。矿化生物膜可能对草食动物和机械损伤具有保护功能。在2685研究单位的框架内，将在项目C3中研究自然环境和水族馆中这种生物膜的形成。在项目C4中，将阐明生物膜形成背后的复杂过程，包括哪些条件以及哪些细菌或真菌可以导致矿物质沉淀或叶组织降解。为此，将从生物膜中分离细菌和真菌物种的个体菌株。这些微生物将在无菌实验室条件下与树叶一起孵育，并分析它们对树叶保存或腐烂的影响。一旦形成生物膜，将测试哪些离子浓度或哪些代谢过程（磷酸盐的释放，尿素的分解，铁的氧化）是由细菌进行的，作为矿物质沉淀在叶子上的先决条件。我们第一个资助期的结果也表明，微生物的衰变活动必须停止或减缓，以便微生物化能够继续。这可能发生在沉积物中沉积之后，可能是通过在缺氧条件下细菌产生的酸释放重金属。因此，将在实验室中研究重金属对生物膜的影响，以建立叶片生物膜化早期阶段的机理模型。