Lactobacillus switches the production of pseudo-cobalamin to vitamin-B12 in the absence of purines.

ELEAN, MARIANO; TORRES, C; HEBERT, EM; FONT, G.; SAAVEDRA, L; TARANTO, MP

Paraná

Congreso; 54TH Annual Meeting Argentine Society for Biochemistry and Molecular Biology- LIV Reunion Annual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2018

SAIB

Lactobacillus coryniformis CRL 1001 and L. reuteri CRL 1098 have the complete gene machinery and synthesize pseudo-cobalamin as final product in a vitamin B12 free commercial medium. Unlike vitamin-B12 (the most biologically active form), the pseudo-cobalamin contains adenine instead of 5,6-dimethlbenzimidazole (DMB) in the Coa-ligand. Considering the vitamin B12-gene clusters of these bacteria, the aim of this work was to analyzed the production of corrinoids with DMB (vitamin B12) instead of adenine (pseudo-B12) as lower ligand base in a vitamin B12 free chemically defined medium (CDM) without purines. Genome-wide screening of genes related to purine metabolism showed that both strains possess all pur genes necessary for the synthesis of inositol monophosphate, the main precursor for purine biosynthesis. Accordingly, both strains were able to grow in B12 free CDM without purines, with the supplementation of different synthetic intermediaries. Isolated compounds with positive B12 activity were quantified and characterized by LC/MS-MS. Total corrinoids values were higher for both strains in comparison to those obtained in vitamin B12 free commercial medium. Interestingly, CRL 1001 strain synthesized cobalamin, suggesting that this strain is able to activate DMB as nitrogenous base instead adenine when it is in excess in a purine-free medium. This is the first demonstration of a metabolic shift to produce vitamin B12 in Lactobacillus. *Both authors contributed equally