Frankia sp. strains form N2-fixing root nodules on woody trees and shrubs in a symbiosis known as “actinorhizal”. Because Frankia strains fix nitrogen, actinorhizal plants grow well on marginal soils. The plants are potential sources of biomass for energy generation and carbon sequestration, and have been used for remediating stressed or contaminated soils. Frankia form the major nitrogen-fixing symbioses in the temperate forests of the world and have immense untapped potential to contribute to DOE’s energy production, waste remediation, and cleanup missions.
The Frankia strains selected for sequencing represent isolates from diverse habitats and environments. These isolates come from four continents (North America, South America, Africa, and Asia) and different habitats, including dry soils with high salinity levels, steppe-like plains at 900 m, and mountain forests at 3,000 m. Four of the strains (EuI1c, BCU110501, R43, and BMG5.12) are members of one of the major lineages (Cluster 3 phylogroup) within the genus and have a broad host range and unique traits including different metal tolerances. The fifth genome is a representative of the another major lineage (Cluster 1 phylogroup) that is more restrictive in its host plant range.
The genomes of Frankia strains from Cluster 3 are about 8-9 million base pairs in length. Their genome complexity reflects the novel developmental attributes of Frankia, their symbiotic and saprophytic lifestyles, and their physiological self-sufficiency (prototrophy). DNA sequence information generated by this project will provide researchers studying actinomycete biology and plant symbioses, as well as Frankia biology, with a wealth of information and tools for years to come.
Principal Investigators: Louis S. Tisa (Univ. of New Hampshire) and Arnab Sen (Univ. of North Bengal)