Size and Diversity of Frankia Populations in Soil

弗兰克氏菌是固氮菌，孢子形成菌，革兰氏阳性菌， 能够形成根的丝状细菌（放线菌目） 在各种主要为木本的多年生植物上的根瘤， 包括桤木和Ceanothus。 这些辐射根联合体 贡献了大量的氮（50-150 Kg N ha-1 ya-1）为温带森林生态系统。 除了增强 通过固氮作用的森林生产力，一些放线菌 植物，如太平洋西北部的赤杨， 重要的木材资源。 Frankia的生态学研究 土壤处于婴儿期，主要是因为 从土壤中分离Frankia并鉴别Frankia 从彼此和其他土壤微生物中分离菌株。 没有 Frankia已经从Ceanothus中分离出来，Ceanothus是一种重要的 俄勒冈州的森林生产力。 即使是桤木， 大多数菌株已被分离出来， 目前还不能培养。 为了评估土壤中Frankia的多样性， 需要开发有效的DNA提取方法， 区分Frankia菌株的方法。 本研究 将量化并可能改善土壤DNA提取 效率 它还将开发一种区分 在Alnus感染的Frankia菌株中， rrn基因的DNA序列。

Frankia are N2-fixing, sporulating, gram positive, filamentous bacteria (Actinomycetales) capable of forming root nodules on a variety of predominantly woody perennial plants, including Alnus and Ceanothus. These actinorhizal associations contribute significant quantities of nitrogen (50-150 Kg N ha-1 ya-1) to temperate forest ecosystems. In addition to enhancing forest productivity via nitrogen fixation, some actinorhizal plants, such as Alnus rubra in the Pacific Northwest, are important timber resources. Ecological studies of Frankia in soil are in their infancy, primarily because of the difficulty of isolating Frankia from soil and of differentiating Frankia strains from each other and from other soil microorganisms. No Frankia have been isolated from Ceanothus, a plant important to forest productivity in Oregon. Even alder, from which the majority of strains have been isolated, harbors many strains which cannot be cultured at this time. In order to assess the diversity of Frankia in soil, it is necessary to develop efficient methods of DNA extraction and a means of distinguishing among Frankia strains. This research will quantify and potentially improve soil DNA extraction efficiency. It will also develop a means of differentiating among Alnus-infective Frankia strains based on differences in the DNA sequence of rrn gene.