College or School
Biochemistry, Molecular & Cellular Biology; Sustainable Agriculture & Food Systems
Faculty Research Advisor
Second Faculty Research Advisor
Actinorhizal plants are woody dicotyledons from eight families that form symbiotic root nodules with the genus Frankia, nitrogen-fixing actinobacteria. Recent studies have found that actinorhizal nodules contain other bacterial inhabitants besides Frankia. The roles that members of the actinorhizal microbiome play are largely unknown. In this study, several bacterial strains were isolated from alder (Alnus) nodules growing at Adam’s Point in Durham, NH in spring 2018 and 2019. These isolates were tested for chemotactic/chemotropic properties and their impacts on alder seedlings and nodulation. A chemotaxis/chemotropism assay was developed to detect the response of these bacteria to actinorhizal root exudates. Additionally, sterile Alnus glutinosa seedlings grown under nitrogen-deficient conditions were inoculated with bacterial isolates alone or in co-culture with Frankia to assess impacts on plant health. For the chemotaxis assay, a few strains including Kocuria, Curtobacterium, Streptomyces, and Herbaspirillum, exhibited differences in motility or produced crystals depending on conditions. The Streptomyces isolate and one of the Kocuria strains exhibited attraction to root exudates from the actinorhizal plant Eleagnus angustifolia, and A. glutinosa to a lesser extent. Preliminary plant studies suggest Streptomyces strain 23 decreased nitrogen stress symptoms in A. glutinosa, and the Streptomyces and Bacillus isolates may play a role in promoting secondary root formation.
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Mercurio, Kelsey C.; Davis, Ian; Pesce, Céline; Swanson, Erik; and Tisa, Louis, "Frankia & Friends: Roles of Various Nodule Inhabitants in the Actinorhizal Symbiosis" (2020). Undergraduate Research Conference (URC) Student Presentations. 482.