Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA, USA.
ISME J. 2010 Jan;4(1):98-110. doi: 10.1038/ismej.2009.91. Epub 2009 Aug 13.
Microbial mats in sulfidic cave streams offer unique opportunities to study redox-based biogeochemical nutrient cycles. Previous work from Lower Kane Cave, Wyoming, USA, focused on the aerobic portion of microbial mats, dominated by putative chemolithoautotrophic, sulfur-oxidizing groups within the Epsilonproteobacteria and Gammaproteobacteria. To evaluate nutrient cycling and turnover within the whole mat system, a multidisciplinary strategy was used to characterize the anaerobic portion of the mats, including application of the full-cycle rRNA approach, the most probable number method, and geochemical and isotopic analyses. Seventeen major taxonomic bacterial groups and one archaeal group were retrieved from the anaerobic portions of the mats, dominated by Deltaproteobacteria and uncultured members of the Chloroflexi phylum. A nutrient spiraling model was applied to evaluate upstream to downstream changes in microbial diversity based on carbon and sulfur nutrient concentrations. Variability in dissolved sulfide concentrations was attributed to changes in the abundance of sulfide-oxidizing microbial groups and shifts in the occurrence and abundance of sulfate-reducing microbes. Gradients in carbon and sulfur isotopic composition indicated that released and recycled byproduct compounds from upstream microbial activities were incorporated by downstream communities. On the basis of the type of available chemical energy, the variability of nutrient species in a spiraling model may explain observed differences in microbial taxonomic affiliations and metabolic functions, thereby spatially linking microbial diversity to nutrient spiraling in the cave stream ecosystem.
硫化洞穴溪流中的微生物席为研究基于氧化还原的生物地球化学养分循环提供了独特的机会。以前来自美国怀俄明州下凯恩洞的工作主要集中在微生物席的有氧部分，这些微生物席主要由假定的化能自养、硫氧化菌属中的 ε 变形菌纲和 γ 变形菌纲组成。为了评估整个微生物席系统中的养分循环和周转率，采用了多学科策略来表征微生物席的厌氧部分，包括全循环 rRNA 方法、最可能数方法以及地球化学和同位素分析的应用。从微生物席的厌氧部分中提取了 17 个主要的细菌分类群和 1 个古菌分类群，这些分类群主要由 δ 变形菌纲和未培养的绿弯菌门成员组成。应用养分螺旋模型，根据碳和硫养分浓度评估微生物多样性从上游到下游的变化。溶解态硫化物浓度的变化归因于硫化物氧化微生物群的丰度变化以及硫酸盐还原微生物的出现和丰度变化。碳和硫同位素组成的梯度表明，上游微生物活动释放和再循环的副产物化合物被下游群落吸收。根据可用化学能的类型，螺旋模型中养分物质的可变性可以解释观察到的微生物分类群和代谢功能的差异，从而将微生物多样性与洞穴溪流生态系统中的养分螺旋空间联系起来。
