Microbial control of mineralization processes in non-marine biofilms

非海洋生物膜矿化过程的微生物控制

• 批准号: 5446864
• 负责人: Professor Dr. Gernot Arp
• 金额: --
• 依托单位: Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2005
• 资助国家: 德国
• 起止时间: 2004-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/5446864?language=en
• 关键词: Microbial; control; mineralization; processes; non

Contrary to calcified biofilms from hardwater creeks where calcification occurs in the top layer of the biofilm due to high cyanobacterial and algal photosynthetic activity calcification in microbial mats from hypersaline lakes on Kiritimati is observed in the deeper mat parts while phototrophic mat layers remain largely uncalcified. Until now it is unclear which non-phototrophic prokaryotes inhibit calcification in the upper parts of the mat or promote biochemical processes leading to exopolymer degradation at the anoxic bottom layer and CaCO3 precipitation in the basal mat parts. Identification of microorganisms inhabiting different zones of hypersaline microbial mats will allow clarifying the prokaryotic contribution to fabric formation via exopolymer production and degradation in dependency of external physicochemical parameters (pCO2, pH buffering, mineral saturation). This addresses to the hypothesis that certain microbialite fabrics traceable in the fossil record only occur as a result of heterotrophic activity, while a photosynthesis-controlled precipitation results in tubular cyanobacterial microfossils.In this following application period we first of all focus on the identification of phototrophic prokaryotic communities in different sub layers of microbial mats, i.e. Cyanobacteria and Purple Bacteria with a main focus on EPS producing organisms. We will characterize a selection of obtained strains which have no known close relative, in order to determine their taxonomic status. Genome sequences should be determined especially for isolates with ecological relevance. One main goal of the future work will be to clarify the origin and identity of the so-called „Black Pebbles“ in the transparent jelly top mat layer ("Froschlaich”) using microbial and chemical analyses. Furthermore, we would like to identify present decomposer communities in different sub layers of microbial mats, i.e. aerobic and anaerobic microorganisms (e.g. sulfate reducing bacteria, methanogens) to understand calcification processes within the mats. After identification of microorganisms we will demonstrate their in situ abundances and will reveal their spatial distribution pattern in relation to carbonate precipitates in thin mat sections and biofilm-veneered microbialite parts by fluorescence in situ hybridizations. In addition, we will compare microbial populations and in situ activities (using available pure cultures) to understand fundamental relationships between microbial exopolymer production/degradation, microbialite formation and environmental parameters. This will be done by stable isotope probing (SIP) which allows linking the phylogeny of organisms to their function. In addition, microcosm experiments with defined artificial mixtures of isolated bacteria will be used to study biomineralization in vitro. A further way to get an impression of the metabolic active fraction of the microbial community in distinct layers of the mat will be obtained by a metaproteomic analysis of mat samples which is planned in cooperation with the Helmholtz Centre for Infection Research in Braunschweig. As a culture-independent approach to identify functions characteristic for the different layers of the microbial mats metagenomic (bar-coded pyrosequencing of 16S rRNA genes) and metatranscriptomic approaches will be employed as well. In addition, investigation of changes in prokaryotic diversity and community composition will be conducted as well as the identification of taxon-specific patterns associated with different layers in microbial mats and biogeographical effects on bacterial community structures by analyzing mats from different lakes. The analyses of ooid-like spherulites, which form in oxygenic mats parts prior to exopolymer degradation and aragonite microbialite formation, may provide significant information with respect to ooid formation. The ooid-like spherulites migrate from their place of nucleation to lower mat parts, where they from part of friable sediments and microbialites. Microfacies, petrographic, isotopic (including 14C-dating), and biogeochemical characterization of the microbialites will constitute a fundamental task to assess the relationship between microbial activity, organic matter and mineral products, also in order to enlarge the understanding of fabrics and facies of ancient microbialites. Analysis of hydrochemical parameters of lake, seepage, microbial mat, and sedimentary pore waters on Kiritimati will be continued in addition to the ongoing investigation of karst water creeks to reveal the general hydro-chemical prerequisites for mineral precipitation, relevance of seepage influxes, and the effect of mi-crobial activities with regard to mineral saturation and growth.

与硬水小溪的钙化生物膜相反，由于高蓝藻和藻类光合作用活性，钙化发生在生物膜的顶层，在Kiritimati的高盐度湖泊的微生物垫中观察到钙化，而光合垫层在很大程度上保持未钙化。到目前为止，它是不清楚的非光养原核生物抑制钙化在垫的上部或促进生化过程导致外聚合物降解在缺氧底层和CaCO 3沉淀在基底垫部分。鉴定栖息在高盐微生物垫的不同区域的微生物将允许澄清原核生物通过依赖于外部物理化学参数（pCO 2、pH缓冲、矿物质饱和度）的外聚合物产生和降解对织物形成的贡献。这解决了化石记录中某些可追溯的微生物组构仅作为异养活动的结果而出现的假设，而光合作用控制的沉淀导致管状蓝藻微化石。在接下来的应用阶段，我们首先专注于鉴定微生物垫不同亚层中的光养原核生物群落，即蓝细菌和紫色细菌，主要关注EPS生产生物体。我们将描述一个选择获得的菌株，没有已知的近亲，以确定其分类地位。基因组序列应确定，特别是与生态相关的分离物。未来工作的一个主要目标将是通过微生物和化学分析来澄清透明果冻顶部垫层（“Froschlaich”）中所谓的“黑色鹅卵石”的来源和身份。此外，我们想确定目前的分解者社区在不同的子层的微生物垫，即好氧和厌氧微生物（如硫酸盐还原菌，产甲烷菌），以了解钙化过程中垫。微生物鉴定后，我们将证明其在原位丰度，并将揭示其空间分布模式的关系，碳酸盐沉淀物在薄垫部分和生物膜贴面microbialite部分荧光原位杂交。此外，我们将比较微生物种群和原位活动（使用可用的纯培养物），以了解微生物胞外聚合物的生产/降解，微生物岩形成和环境参数之间的基本关系。这将通过稳定同位素探测（SIP）来完成，该探测允许将生物体的发育与其功能联系起来。此外，将使用确定的分离细菌的人工混合物的微观实验来研究体外生物矿化。通过与布伦瑞克的Helmholtz感染研究中心合作计划的垫样品的元蛋白质组学分析，将获得对垫的不同层中的微生物群落的代谢活性部分的印象的另一种方法。作为鉴定微生物垫的不同层的功能特征的不依赖于培养物的方法，还将采用宏基因组学（16 S rRNA基因的条形码焦磷酸测序）和元转录组学方法。此外，原核生物多样性和社区组成的变化将进行调查，以及与不同层次的微生物垫和细菌群落结构分析垫从不同的湖泊的地理学影响的分类特定模式的识别。类卵状体球晶，形成在含氧垫部分之前，外聚合物降解和文石微生物形成的分析，可以提供重要的信息，相对于类卵状体的形成。类卵粒状球粒从成核处迁移到下部席状部分，在下部席状部分形成部分易碎沉积物和微生物岩。微生物岩的微相、岩相学、同位素（包括~（14）C定年）和地球化学特征将是评价微生物活动、有机质和矿物产物之间关系的基础性工作，也是扩大对古微生物岩组构和相的认识的基础。除了正在进行的岩溶水小溪调查外，还将继续分析Kiritimati的湖泊、渗漏、微生物垫和沉积孔隙沃茨的水化学参数，以揭示矿物沉淀的一般水化学先决条件、渗漏流入的相关性以及微生物活动对矿物饱和度和生长的影响。