Havemann Stephanie A, Foster Jamie S
Department of Microbiology and Cell Science, University of Florida, Space Life Sciences Laboratory, Kennedy Space Center, FL 32899, USA.
Appl Environ Microbiol. 2008 Dec;74(23):7410-21. doi: 10.1128/AEM.01710-08. Epub 2008 Oct 3.
Microbialites are organosedimentary structures that result from the trapping, binding, and lithification of sediments by microbial mat communities. In this study we developed a model artificial microbialite system derived from natural stromatolites, a type of microbialite, collected from Exuma Sound, Bahamas. We demonstrated that the morphology of the artificial microbialite was consistent with that of the natural system in that there was a multilayer community with a pronounced biofilm on the surface, a concentrated layer of filamentous cyanobacteria in the top 5 mm, and a lithified layer of fused oolitic sand grains in the subsurface. The fused grain layer was comprised predominantly of the calcium carbonate polymorph aragonite, which corresponded to the composition of the Bahamian stromatolites. The microbial diversity of the artificial microbialites and that of natural stromatolites were also compared using automated ribosomal intergenic spacer analysis (ARISA) and 16S rRNA gene sequencing. The ARISA profiling indicated that the Shannon indices of the two communities were comparable and that the overall diversity was not significantly lower in the artificial microbialite model. Bacterial clone libraries generated from each of the three artificial microbialite layers and natural stromatolites indicated that the cyanobacterial and crust layers most closely resembled the ecotypes detected in the natural stromatolites and were dominated by Proteobacteria and Cyanobacteria. We propose that such model artificial microbialites can serve as experimental analogues for natural stromatolites.
微生物岩是由微生物席群落对沉积物进行捕获、粘结和石化作用而形成的有机沉积结构。在本研究中，我们从巴哈马群岛埃克苏马海峡采集的一种微生物岩——天然叠层石中，开发出了一种模拟人工微生物岩系统。我们证明，人工微生物岩的形态与天然系统一致，即存在一个多层群落，其表面有明显的生物膜，顶部5毫米处有一层密集的丝状蓝细菌，地下有一层由融合鲕粒砂粒组成的石化层。融合颗粒层主要由碳酸钙多晶型文石组成，这与巴哈马叠层石的成分相对应。还使用自动核糖体基因间隔区分析（ARISA）和16S rRNA基因测序，比较了人工微生物岩和天然叠层石的微生物多样性。ARISA分析表明，两个群落的香农指数相当，人工微生物岩模型中的总体多样性并没有显著降低。从三个人工微生物岩层和天然叠层石中各自生成的细菌克隆文库表明，蓝细菌层和外壳层与天然叠层石中检测到的生态型最为相似，且以变形菌门和蓝细菌为主导。我们认为，这种模拟人工微生物岩可作为天然叠层石的实验类似物。
