Mechanisms of Calcium Carbonate Precipitation and Dissolution: Microbial Populations, Metabolic Processes and Mineral Products

本项目通过对巴哈马群岛Eleuthera高盐池塘微生物垫中从岩化到非岩化微生物群落的梯度进行地质生物学研究，研究了生物活性沉积物中碳酸盐沉淀的潜在机制。现场测量和现场操作与各种实验室实验相结合，以分离和表征控制碳酸盐沉淀的生物过程和环境变量。pi正在研究与碳酸盐矿物形成有关的微生物群落组成、代谢率和EPS特征。正在研究的环境参数包括水化学（例如pH、[Ca2+]、[CO32-]）和光强度。微生物代谢（无机碳的生产/消耗）在碳酸盐沉淀正在进行研究，通过试验纯和混合细菌培养在批培养和连续培养。通过关注从石化垫到富含eps的凝胶状垫的自然梯度的沉淀和溶解，PIs希望了解微生物群落支配碳酸钙沉淀的一般规律。这一信息正被用于发展一种描述生物活性沉积物中矿物沉淀的机械理论。由于在许多环境中都发现了导致碳酸盐沉淀的主要微生物行业（蓝藻、硫氧化剂、硫酸盐还原剂），因此所开发的理论将解决整个碳酸盐工厂、微生物在地质上重要矿物产品形成中的作用以及生物材料的石化和保存。

Visscher Abstract This project is investigating the underlying mechanisms of carbonate precipitation in biologically active sediments by performing a geobiological study on a gradient from lithifying to non-lithifying microbial communities from microbial mats in a hypersaline pond (Eleuthera, Bahamas). Field measurements and in situ manipulations are being combined with a variety of laboratory experiments to isolate and characterize the biological processes and environmental variables that control carbonate precipitation. The PIs are examining microbial community composition, metabolic rates, and EPS characteristics in relation to carbonate mineral formation. Environmental parameters which are being investigated include water chemistry (e.g., pH, [Ca2+], [CO32-]) and light intensity. Microbial metabolism (production/consumption of inorganic carbon) on carbonate precipitation are being investigated by experimenting with pure and mixed bacterial cultures in both batch and continuous culture. By focusing on precipitation and dissolution along a natural gradient from lithifying mats to gelatinous EPS-rich mats, the PIs hope to understand the general rules that govern calcium carbonate precipitation by microbial communities. This information is being used to develop a mechanistic theory describing mineral precipitation in biologically active sediments. Since the main microbial guilds (cyanobacteria, sulfur oxidizers, sulfate reducers) responsible for carbonate precipitation are found in numerous environments, the theory developed will address the entire carbonate factory, the role of microbes in the formation of geologically important mineral products and the lithification and preservation of biological materials.