University Archives

Duckweed (Lemnoideae) are small floating aquatic plants native to Michigan.  Despite its diminutive size, duckweed has high net primary productivity and biomass in aquatic ecosystems because of its rapid clonal reproduction.  As a result, duckweed is used in phytoremediation strategies to mitigate nutrient pollution.  Microbial symbiosis plays an important role in plant nutrient absorption.  Most of the plant-microbe interaction studies focus on land plants.  In this study, bacteria that form symbiotic relationships with duckweed will be investigated to determine their role in nutrient uptake by aquatic plants.

               A metabarcoding study of giant duckweed (Spirodela polyrhiza) has shown that bacteria in the Rhizobiaceae preferentially accumulate in the plant biofilm.   To study these bacteria, a semi-selective medium was used to isolate putative members of the Lemnoideae.  Three duckweed species (Limna minor, S. polyrhiza, and Wolffia columbiana) were collected from the Lake Saint Clair watershed and homogenized.  Exudate was plated on Yeast Extract Mannitol (YEM) medium supplemented with calcofluor white and Congo red.   Bacterial colonies that were fluorescent (putative Rhizobium sp.) or red (putative Agrobacterium sp.) were isolated.  Their identity was confirmed by sequencing the 16S rRNA encoding PCR amplicons.  The following Rhizobiaceae bacteria have been isolated: Agrobacterium sp., Rhizobium sp., and Peteryoungia sp.  Their genomes will be sequenced to help elucidate the role these bacteria play in aquatic plant – bacterial interactions.