Composition and diversity of Medicago truncatula root bacterial endophyte populations resulting from growth in different Oklahoma soils

Scope and method of study: Differences in composition and diversity of the Medicago truncatula root bacterial endophyte population resulting from growth in six diverse soils and one commercial growing medium were evaluated by cloning and sequencing of 16S rDNA amplification products and temperature gradient gel electrophoresis (TGGE) of 16S rDNA fragments.;Findings and conclusions: Cloning and sequencing of 16S rDNA revealed 36 genera of bacteria encompassing five phyla as putative M. truncatula root endophytes. Plants grown in two acidic soils with a forest background and a commercial growing medium possessed the highest endophyte diversity. Moderate diversity was observed in plants grown in three managed agricultural soils. Endophyte diversity was lowest in plants grown in soil collected from an undisturbed native tallgrass prairie. TGGE failed to adequately resolve the endophytic bacterial 16S rDNA fragments and 16S rDNA bands on the silver-stained TGGE gel could not be sequenced or cloned into plasmid vectors for identification.