A first study for the establishment of a source of vitamin B12 as of the genetic modification of the Cyanobacteria Arthrospira platensis

Tutor: Marc GüellCobalamin de novo synthesis appears to be restricted solely to some bacteria and archaea. In humans, this nutrient is usually acquired through the consumption of animal products. However, it can lead to a vitamin B12 deficiency in people with plant-based lifestyle where the consumption of animal products is minimal. Therefore, we investigated in this study the possibility of creating a source of cobalamin from cyanobacteria, a photosynthetic and non-nitrogen-fixing blue-green algae. Arthrospira platensis, an edible cyanobacteria, can produce a pseudovitamin B12 but lack enzymes involved in the production of the active variant which can be metabolized by humans and used as a vitamin B12 source. Therefore, we compared the metabolic pathways of the pseudovitamin B12 synthesized in the cyanobacteria Arthrospira platensis with the canonical synthetic pathways of vitamin B12 discovering that the cobT, cobC and cobS genes, key players in the binding of the lower ligand characteristic of vitamin B12, are the main proteins absent in the metabolic pathways of cyanobacteria. Subsequently, we designed a transformation system based on Tn5 transposition that could bridge the differences between the two pathways. For this purpose, the genes cblT and cblS, from the thermophilic bacillus Geobacillus (G.) Kaustophilus with the ability shown to substitute the action of the cob genes in other species, have been selected to constitute the Tn5 transposon, as well as a resistance to the antibiotic spectinomycin