The present invention to the identification of a novel isolated bacterial strain, the Limosilactobacillus reuteri strain which is characterized by a naturally occurring overproduction of riboflavin (vitamin B2) compared to other known strains of lactobacilli. Said strain of the Limosilactobacillus species is deposited under accession number LMG P-32020. In a further aspect, also the uses of said L. reuteri strain are disclosed herein. In particular, the use of said strain in food and feed industry, human and veterinary health, large-scale vitamin production, cosmetics and consumer care products is disclosed.

The present disclosure provides variant Listeria bacteria that lack functional ribC and ribF genes. Also provided are methods of making and using the variant Listeria bacteria, e.g., as vectors, vaccines, and therapeutics. The present disclosure provides variant Listeria bacteria that provide for production of a Mucosal-Associated Invariant T (MAIT) cell ligand in vivo. Also provided are methods of making and using the variant Listeria bacteria, e.g., to stimulate and expand the number of MAIT cells in an individual.