Analysis of a Eukaryotic Microbial Mat Community Across Environmental Gradients in a Thermal, Acidic Stream

热酸性流中跨环境梯度的真核微生物垫群落分析

• 批准号: 9977922
• 负责人: Joan Henson
• 金额: $ 86.05万
• 依托单位: Montana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-09-01 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9977922&HistoricalAwards=false
• 关键词: Analysis; Eukaryotic; Microbial; Mat; Community

9977922The eukaryotic microbial mat at Nymph Creek in Yellowstone National Park is an ideal natural laboratory for a Microbial Observatory designed to increase our understanding of eukaryotic microbial genetic diversity, ecophysiology, and behavior. The thermal (50 degrees C), acidic (pH 2.7) water near the stream's source creates stable environmental gradients in temperature, pH, and light over which changes in microbial populations will be monitored. The mat's biocomplexity is limited near the stream's source but includes the red alga Cyanidium caldarium, the most thermophilic alga known, and the thermophilic, filamentous fungus Dactylaria constricta var. gallopava. As downstream pH and water flow increase and temperatures decline, a concomitant expansion of microbial species, including slime molds, protozoa, green algae, and diatoms, is expected. Two Nymph Creek sites, defined in terms of differing light, pH, and temperature, will be extensively monitored over diurnal and seasonal time periods. Contemporary analyses, including microscopic methods and rRNA sequencing, will be used to document microbial diversity and analyze the mat's microstructure at both sites. Changes in macro- and micro-scale environmental conditions in the bulk water and through the vertical aspect of the mats will be recorded. Nucleic acid sequence-based techniques will be used to monitor microbial population changes in situ under environmental conditions that vary in space and time. Ribosomal RNA sequence-based technologies greatly facilitate the study of microbes in natural environments and provide a rational platform on which to base phylogeny. However, while these methods are used routinely to study uncultivated bacterial populations, the same approaches have not been rigorously applied to studies of eukaryotic microbial communities. As a result, the discovery of new eukaryotic species and an understanding of the diversity and ecophysiologies of eukaryotic microorganisms are largely restricted to descriptions of cultivated strains. It is clear that uncultivated eukaryotic microorganisms exist and their discovery may represent a vast untapped source of new microbial products. Therefore, an in-depth study, focused on the ecology of a eukaryotic microbial community, augmented by nucleic acid sequence-based methods of detection and classification, cannot fail to fundamentally advance current knowledge in this field. Information gained from this study will include descriptions of new species, novel strains in axenic culture, and measurements of genetic diversity and its relationship to the ecophysiologies of indigenous microorganisms. Of particular interest is the interaction between C. caldarium and D. constricta, first described in the 1970's by Brock and his coworkers, who found that the alga and the fungus always cohabit. However, they did not elaborate on this interaction, which could be symbiotic, parasitic, or merely coincidental. This pair of organisms may represent a primitive ancestor to modern-day lichens, which are usually composed of a filamentous fungus and a green alga. In-depth studies will explore possible features of the D. constricta-C. caldarium association, including whether the alga provides nutrients for the fungus, whether the fungus parasitizes the alga, and whether the fungal hyphae provide a matrix that anchors the unicellular algae and stabilizes stream sediment. Melanin of fungal hyphae may also protect algae from the harmful effects of intense light. In addition, new genotypes of the fungus or alga detected by rRNA sequencing across environmental gradients will be cultured. The distributions of fungal and algal 18S rRNA genotypes will determine whether unique genotypes correlate with ecological niches. Nymph Creek provides an accessible outdoor laboratory where microbes that form luxuriant bright green microbial mats can be observed by researchers, students and the public. Knowledge from the Nymph Creek observatory will be shared via outreach and internet activities. These activities should increase public awareness and appreciation of microbial diversity, biochemical microbial activities, and their influences on ecosystems.

9977922黄石国家公园宁芙溪的真核微生物垫是微生物观测站的理想天然实验室，旨在增进我们对真核微生物遗传多样性、生态生理学和行为的了解。 溪流源头附近的热水（50 摄氏度）、酸性水（pH 2.7）在温度、pH 和光照方面形成稳定的环境梯度，从而可以监测微生物种群的变化。 该垫子的生物复杂性在溪流源头附近受到限制，但包括红藻Cyanidium caldarium（已知最耐热的藻类）和嗜热丝状真菌Dactylaria constricta var。加洛帕瓦。随着下游 pH 值和水流量的增加以及温度的下降，预计粘菌、原生动物、绿藻和硅藻等微生物种类也会随之增加。根据不同的光照、pH 值和温度定义的两个 Nymph Creek 地点将在昼夜和季节性时间段内得到广泛监测。现代分析，包括显微方法和 rRNA 测序，将用于记录微生物多样性并分析两个地点垫子的微观结构。将记录大量水中以及通过垫子的垂直方向的宏观和微观环境条件的变化。 基于核酸序列的技术将用于监测在空间和时间变化的环境条件下原位微生物种群的变化。基于核糖体 RNA 序列的技术极大地促进了自然环境中微生物的研究，并为系统发育提供了一个合理的平台。然而，虽然这些方法通常用于研究未培养的细菌种群，但相同的方法尚未严格应用于真核微生物群落的研究。因此，新真核物种的发现以及对真核微生物多样性和生态生理学的理解在很大程度上仅限于对培养菌株的描述。很明显，存在未培养的真核微生物，它们的发现可能代表了新微生物产品的巨大未开发来源。因此，专注于真核微生物群落生态学的深入研究，并通过基于核酸序列的检测和分类方法进行增强，必然会从根本上推进该领域的现有知识。从这项研究中获得的信息将包括新物种的描述、无菌培养中的新菌株以及遗传多样性的测量及其与本土微生物生态生理学的关系。 特别令人感兴趣的是 C. caldarium 和 D. constricta 之间的相互作用，Brock 和他的同事在 1970 年代首次描述了这种相互作用，他们发现藻类和真菌总是共存。 然而，他们没有详细说明这种相互作用，这种相互作用可能是共生的、寄生的，或者仅仅是巧合。 这对生物体可能代表了现代地衣的原始祖先，现代地衣通常由丝状真菌和绿藻组成。 深入研究将探索 D. constricta-C 的可能特征。高温关联，包括藻类是否为真菌提供营养，真菌是否寄生于藻类，以及真菌菌丝是否提供了锚定单细胞藻类并稳定河流沉积物的基质。真菌菌丝的黑色素还可以保护藻类免受强光的有害影响。此外，还将培养通过跨环境梯度的 rRNA 测序检测到的真菌或藻类的新基因型。真菌和藻类 18S rRNA 基因型的分布将决定独特的基因型是否与生态位相关。 Nymph Creek 提供了一个方便的户外实验室，研究人员、学生和公众可以在这里观察形成茂盛的亮绿色微生物垫的微生物。 Nymph Creek 天文台的知识将通过外展和互联网活动进行分享。这些活动应提高公众对微生物多样性、生化微生物活动及其对生态系统影响的认识和了解。