Laguna Bacalar is a sulfate‐rich freshwater lake on the Yucatan Peninsula that hosts large microbialites. High sulfate concentrations distinguish Laguna Bacalar from other freshwater microbialite sites such as Pavilion Lake and Alchichica, Mexico, as well as from other aqueous features on the Yucatan Peninsula. While cyanobacterial populations have been described here previously, this study offers a more complete characterization of the microbial populations and corresponding biogeochemical cycling using a three‐pronged geobiological approach of microscopy, high‐throughput DNA sequencing, and lipid biomarker analyses. We identify and compare diverse microbial communities of Alphaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria that vary with location along a bank‐to‐bank transect across the lake, within microbialites, and within a neighboring mangrove root agglomeration. In particular, sulfate‐reducing bacteria are extremely common and diverse, constituting 7%–19% of phylogenetic diversity within the microbialites, and are hypothesized to significantly influence carbonate precipitation. In contrast, Cyanobacteria account for less than 1% of phylogenetic diversity. The distribution of lipid biomarkers reflects these changes in microbial ecology, providing meaningful biosignatures for the microbes in this system. Polysaturated short‐chain fatty acids characteristic of cyanobacteria account for <3% of total abundance in Laguna Bacalar microbialites. By contrast, even short‐chain and monounsaturated short‐chain fatty acids attributable to both Cyanobacteria and many other organisms including types of Alphaproteobacteria and Gammaproteobacteria constitute 43%–69% and 17%–25%, respectively, of total abundance in microbialites. While cyanobacteria are the largest and most visible microbes within these microbialites and dominate the mangrove root agglomeration, it is clear that their smaller, metabolically diverse associates are responsible for significant biogeochemical cycling in this microbialite system.

中文翻译：

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来自墨西哥Laguna Bacalar的现代淡水微生物的微生物多样性和生物标志物分析。

拉古纳·巴卡拉（Laguna Bacalar）是尤卡坦半岛上富含硫酸盐的淡水湖泊，拥有大量的微辉石。高浓度的硫酸盐使Laguna Bacalar与其他淡水微生物岩位点（如墨西哥的Pavilion Lake和Alchichica）以及尤卡坦半岛的其他含水特征区分开。尽管先前已经描述了蓝细菌种群，但这项研究使用显微镜的三管齐下的生物学方法，高通量DNA测序和脂质生物标志物分析，对微生物种群和相应的生物地球化学循环提供了更完整的表征。我们确定并比较Alphaproteobacteria，Deltaproteobacteria和Gammaproteobacteria的各种微生物群落随沿湖跨岸横断面，微辉石岩内以及邻近的红树林根系群内的位置而变化。尤其是，硫酸盐还原菌极为常见且种类繁多，占微生物岩系内系统发育多样性的7％–19％，并被认为会严重影响碳酸盐的沉淀。相反，蓝细菌不到系统发育多样性的1％。脂质生物标志物的分布反映了微生物生态学的这些变化，为该系统中的微生物提供了有意义的生物特征。蓝细菌特有的多饱和短链脂肪酸占Laguna Bacalar微恶岩中总丰度的<3％。相比之下，即使是短链和单不饱和短链脂肪酸也可归因于蓝细菌和许多其他生物，包括丙型杆菌和丙型杆菌分别占微辉石岩总丰度的43％–69％和17％–25％。尽管蓝细菌是这些微生物体中最大，最可见的微生物，并且主导着红树林的根团聚，但很显然，它们较小的，代谢多样的同伴是该微生物体系统中重要的生物地球化学循环的原因。