Ca-carbonates precipitation and limestone genesis -: the microbiogeologist point of view
Ca-carbonates precipitation and limestone genesis -: the microbiogeologist point of view
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DOI：
10.1016/s0037-0738(99)00028-7
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发表时间：
1999-07-01
影响因子：
2.8
通讯作者：
Perthuisot, JP
中科院分区：
文献类型：
--
作者：
Castanier, S;Le Métayer-Levrel, G;Perthuisot, JP
实验表明，异养细菌产生碳酸盐颗粒遵循不同的途径。在异养中，被动碳酸化作用是通过改变培养基产生的，导致碳酸根和碳酸氢根离子的积累以及固体颗粒的沉淀。它是由氮循环（氨基酸的氨化，尿素和尿酸的降解，硝酸盐的异化还原）和硫循环（硫酸盐的异化还原）的几种代谢途径诱导的。活性碳酸化作用与上述代谢途径无关。碳酸盐颗粒是通过离子交换通过细胞膜以下仍然知之甚少的机制，在自养，非甲基营养甲烷和蓝藻光合作用也可能有助于碳酸盐（自养碳酸盐）的沉淀。由于碳酸化作用既不局限于特定的细菌分类群，也不局限于特定的环境，因此自前寒武纪以来，它一直是一种普遍存在的现象。碳酸盐生成是异养细菌群落对环境中有机物富集的反应。经过一段潜伏期后，细菌数量呈指数级增加，代谢终产物也随之积累。这些诱导pH升高以及培养基中碳酸根和碳酸氢根离子的积累。当大部分初始富集被消耗并且细菌种群的死亡和生长之间达到平衡时，该阶段结束于稳定状态。颗粒碳酸化发生在指数阶段，并或多或少在稳态开始后结束。主动碳酸化作用似乎首先开始，然后是被动碳酸化作用，它诱导最初产生的颗粒的生长。在富营养条件下，第一固体产物是出现在细菌体表面上的斑块，并聚结直到形成从细胞排出的刚性涂层和/或颗粒。所有这些微小的颗粒聚集成生物矿物聚集体，通常显示出“预结晶”结构。这些聚集体生长并形成生物晶体积聚，其随着生长逐渐显示出更多的晶体结构。在贫营养条件下，初级固体产物在晶体结构中迅速平滑，不留任何痕迹。在目前的水环境中，除了深海之外，异养细菌碳酸盐生成在碳酸钙沉积中的潜在效率远高于自养或非生物过程。它更有可能占广泛的明显非生物石灰岩形成比任何后者。就生物碎屑颗粒而言，可以观察到，生物体的外壳和外壳是由细胞器官的活动构成的，而细胞器官现在被许多生物学家认为是内共生细菌。因此，除了（可能是神话）纯粹的异养和自养石灰岩，大多数石灰岩必须被认为是主要的异养细菌的起源。由于石灰岩中的碳是由有机质释放的，因此细菌异养成碳作用是地球演化过程中大气-岩石圈关系的一个基本现象。(C)1999 Elsevier Science B. V.保留所有权利。
Experiments show that the production of carbonate particles by heterotrophic bacteria follows different ways. In heterotrophy, the passive carbonatogenesis is generated by modifications of the medium that lead to the accumulation of carbonate and bicarbonate ions and to the precipitation of solid particles. It is induced by several metabolic pathways of the nitrogen cycle (ammonification of amino-acids, degradation of urea and uric acid, dissimilatory reduction of nitrates) and of the sulphur cycle (dissimilatory reduction of sulphates), The active carbonatogenesis is independent of the mentioned metabolic pathways. The carbonate particles are produced by ionic exchanges through the cell membrane following still poorly known mechanisms, In autotrophy, non-methylotrophic methanogenesis and cyanobacterial photosynthesis also may contribute to the precipitation of carbonates (autotrophic carbonates). As carbonatogenesis is neither restricted to particular taxonomic groups of bacteria nor to specific environments, it has been an ubiquitous phenomenon since Precambrian times. Carbonatogenesis is the response of heterotrophic bacterial communities to an enrichment of the milieu in organic matter. After a phase of latency, there is an exponential increase of bacterial numbers together with the accumulation of metabolic end-products. These induce a pH increase and an accumulation of carbonate and hydrogenocarbonate ions in the medium. This phase ends into a steady state when most part of the initial enrichment is consumed and there is a balance between death and growth in bacterial populations. Particulate carbonatogenesis occurs during the exponential phase and ends more or less after the beginning of the steady state. The active carbonatogenesis seems to start first and to be followed by the passive one which induces the growth of initially produced particles. In eutrophic conditions, the first solid products are patches that appear on the surface of the bacterial bodies and coalesce until forming a rigid coating and/or particles excreted from the cell. All these tiny particles assemble into biomineral aggregates which often display 'precrystalline' structures. These aggregates grow and form biocrystalline build-ups which progressively display more crystalline structures with growth. In oligotrophic conditions, the primary solid products are rapidly smoothed in the crystalline structure and leave no trace. In present aqueous environments, apart from deep ocean, the potential efficiency of heterotrophic bacterial carbonatogenesis in Ca-carbonate sedimentation is much higher than autotrophic or abiotic processes. It much more likely accounts for extensive apparently abiotic limestone formation than any of the latter. As far as biodetrital particles are concerned, it may be observed that the shells and tests of organisms are built from the activity of cellular organites which are nowadays considered by a number of biologists as endosymbiotic bacteria. Thus, apart from (probably mythical) purely evaporitic and autotrophic ones, most limestones must be considered as principally of heterotrophic bacterial origin. As the carbon of limestones is issued from organic matter, bacterial heterotrophic carbonatogenesis appears as a fundamental phenomenon in the relationships between atmosphere and lithosphere during the biogeological evolution of the Earth. (C) 1999 Elsevier Science B.V. All rights reserved.