Source of Vitamin B12 in plants of the Lemnaceae family and its production by duckweed-associated bacteria

While most plants are not known to contain significant levels of the essential corrinoid cobalamin (vitamin B12), considerable levels of vitamin B12 were found in the duckweed clone Wolffia globosa Mankai. Although endophytes were speculated to be the source of this vitamin B12, it has not been tested yet. In this study, we carried out comparative analysis of vitamin B12 content in 15 duckweed accessions across 11 species. Significant but variable levels of vitamin B12 were found in all unsterile duckweed cultures tested. In contrast, disinfected duckweed cultures with lower levels of bacteria, as monitored by PCR-based methods, contained little vitamin B12. Importantly, two strains of duckweed-associated bacteria were shown to produce vitamin B12. This work provides evidence for bacteria as the source of vitamin B12 in duckweeds. Bioinformatics-aided identification of vitamin B12 producers among duckweed-associated bacteria could facilitate their systematic incorporation into duckweed-based foods to support a planetary health diet.