The invention provides a genetically modified bacterial cell capable of improved iron-sulfur cluster delivery, characterized by a modified gene encoding a mutant Iron Sulfur Cluster Regulator (IscR) as well as one or more transgenes encoding polypeptides that enhance the biosynthesis of either biotin, lipoic acid or thiamine. The invention provides a method for producing either biotin, lipoic acid or thiamine using the genetically modified bacterium of the invention; as well as for the use of the genetically modified bacterial cell for either biotin, lipoic acid or thiamine production.