REU: Microbial Ecology of Anaerobic Cellulose Decomposition

提出的研究目标是促进对土壤和沉积物中厌氧纤维素降解的微生物生态学的理解。目前，对于在缺氧条件下将纤维素（陆地环境中最丰富的有机物质）转化为CO2和CH4的复杂微生物过程知之甚少。该项目的一个重要目标是开发方法来识别、枚举和估计土壤和沉积物中厌氧纤维素分解细菌群的活性。快速RNA测序方法将用于纤维素发酵菌分离菌株的16S核糖体RNA测序。将对序列进行比对，以确定细菌群成员共有的序列。与这些独特序列互补的寡脱氧核苷酸将被用作探针，在对照实验和环境样品中检测特定纤维素分解细菌群的存在和活性。该项目的第二个目标是在马萨诸塞州中部一个拟议的研究地点，使用这些探针调查排水不良的森林土壤中纤维素分解细菌的活性。最后一个目标涉及纤维素发酵细菌固定N2的能力。来自土壤和沉积物的几种细菌菌株最近被证明使用纤维素作为固定N2的能量来源。作为拟议项目的一部分，分离的纤维素发酵细菌菌株，以及目前已知的其他菌株，将被检查是否存在氮酶活性，以确定纤维素发酵细菌中固定N2能力的普遍程度。从而为建立自然环境中碳和氮循环之间的重要联系奠定了基础。这种过程在许多自然系统中很可能是常见的，它们可能是重要生物过程的指示。

The goal of the proposed research is to advance understanding of the microbial ecology of anaerobic cellulose degradation in soils and sediments. At present, little is known of the complex microbial processes responsible for the conversion in the absence of oxygen, of cellulose, the most abundantly- produced organic material in terrestrial environments, to CO2 and CH4. An important objective of the project is to develop methods to identify, enumerate, and estimate the activity of groups of anaerobic cellulolytic bacteria in soils and sediments. Rapid RNA sequencing methodology will be used to sequence 16S ribosomal RNAs of isolated strains of cellulose-fermenting bacteria. Sequences will be aligned to identify those that are shared by members of groups of bacteria. Oligodeoxynucleotides complementary to these unique sequences will be used as probes to detect the presence and activity of specific groups of cellulolytic bacteria in controlled experiments and in environmental samples. A second objective of the project is to use these probes to investigate the activity of cellulolytic bacteria in poorly-drained forest soil at a proposed study site in Central Massachusetts. A final objective concerns the ability of cellulose-fermenting bacteria to fix N2. Several strains of bacteria from soils and sediments have recently been shown to use cellulose as an energy source for the fixation of N2. Strains of cellulose-fermenting bacteria isolated as part of the proposed project, as well as additional presently known strains, will be examined for the presence of nitrogenase activity in order to determine the prevalence of the ability to fix N2 among cellulose-fermenting bacteria, thus setting the groundwork for establishing an important link between carbon and nitrogen cycles in natural environments. Such processes are likely to be common in many natural systems, where they may be indications of important biological processes.