Biological influence on calcification and iron oxide formation

生物矿化过程是微生物为了获得能量和/或其活动对微环境的影响而引发的复杂反应。在之前的资助期间，我们将重点放在微生物介导的铁沉淀法上，将艾斯普哈德岩石实验室作为研究地点。我们使用高通量测序技术对系统中的微生物群落进行了分析，重点分析了铁氧化菌的多样性。我们发现被测试的3个不同含水层所喂养的微生物群落之间存在很大的差异。数据显示，占优势的铁氧化细菌并不是先前假设的加里奥氏菌。在隧道的不同位置发现了不同的优势铁氧化剂(但Gallionella从来不是优势铁氧化剂)。我们发现，大量测量同位素标记的微生物垫低估了铁的氧化速率高达一个数量级。一个原因是体内的铁循环：氧化铁在生物上迅速还原，为铁氧化提供额外的Fe2+。铁的非生物沉淀对成矿作用的贡献率很高，但无法准确量化。在接下来的两年里，我们将重点关注以下问题：1)水化学如何决定铁氧化群落的组成；2)生物膜内非生物铁沉淀的主要成核点是有机物(EPS)还是生物沉淀铁；3)铁循环的实际速率是多少(铁还原与氧化耦合)。

Biomineralization processes are complex reactions induced by microorganisms for energy gain and / or by the effect their activity has on the microenvironment. In the previous funding period we have focused on microbially mediated iron precipitation using the Äspö Hard Rock Laboratory as a study site. We have used high‐throughput sequencing to analyze the microbial community in the system focusing our analysis on the diversity of ironoxidizing bacteria. We found large variations between the microbial communities fed by the 3 different aquifers tested. The data showed that the dominant iron oxidizing bacteria is not Gallionella, as previously assumed. Different dominant iron oxidizer are found at different locations in the tunnel (but Gallionella is never dominant). We found that bulk measure-ments of isotope‐labeled microbial mats underestimates iron oxidation rates by up to an order of magnitude. One reason is the internal iron cycling: oxidized iron is rapidly reduced biologically supplying additional Fe2+ for iron oxidation. The contribution of abiotic precipitation of iron to the mineralization process is high, but could not be accurately quantified. We will focus the coming 2 years on the fol-lowing issues:1) How does water chemistry determine the iron‐oxidizing community composition2) Is organic matter (EPS) or biotically‐precipitated iron the main nucleation site for abiotic iron precipitation within the biofilm3) What is the actual rate of iron cycling (Fe‐reduction coupled to oxidation).The proposed study aims to elucidate which environmental conditions control biotic and abiotic iron mineralization.