Little is known about Frankia, a gram-positive, nitrogen-fixing bacterium, because of the difficulty associated with isolating pure cultures. This nitrogen-fixing symbiosis involves Frankia and the roots of actinorhizal host plants belonging to eight plant families and 25 genera. These plants are important pioneer species traditionally found in nitrogen-poor soils and. disturbed sites. Additionally, many of these plants have economic potential. Because isolation is difficult, the use of molecular biology methods can be quite helpful. This study uses the LH-PCR to study the intergenic spacer region of Frankia sampled both from nodules and the soil bacterial community. Three locations with co-occurring actinorhizal hosts were sampled across the state of Oregon. Three sets of nodules were sampled from each host and a soil sample was taken beneath each host along with an additional soil sample between the two co-occurring hosts. DNA was extracted from these samples and used to perform the LH-PCR. It was determined that soil Frankia communities were more closely related based on geographic location rather than host plant. LH-PCR was able to distinguish between nodules obtained from Ceanothus and Alnus but not between Ceanothus and Purshia. Also, LH-PCR was not able to distinguish any differences between the two species of Ceanothus but did show that Alnus may be infected by two different strains of Frankia. The primers used in this study may have also amplified other bacteria
belonging to Actinomycetales. Further work in cloning and sequencing of the soil samples is needed to determine what organisms were amplified.
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