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.

The invention relates to a genetically modified prokaryotic cell capable of improved iron-sulfur cluster delivery, characterized by a modified gene encoding a mutant Iron Sulfur Cluster Regulator (IscR) and one or more transgenes or upregulated endogenous genes encoding iron-sulfur (Fe—S) cluster polypeptides or proteins that catalyze complex radical-mediated molecular rearrangements, electron transfer, radical or non-redox reactions, sulfur donation or perform regulatory functions. The prokaryotic cells are characterized by enhanced activity of these iron-sulfur (Fe—S) cluster polypeptides, enhancing their respective functional capacity, and facilitating enhanced yields of compounds in free and protein-bound forms, including heme, hemoproteins, tetrapyrroles, B vitamins, amino acids, δ-aminolevulinic acid, biofuels, isoprenoids, pyrroloquinoline quinone, ammonia, indigo, or their precursors, whose biosynthesis depends on their activity. The invention further relates to a method for producing said compounds or their precursors using the genetically modified prokaryotic cell of the invention, and the use of the genetically modified prokaryotic cell.

The invention provides a genetically modified bacterium for production of thiamine; where the bacterium is characterized by a transgene encoding a thiamine monophosphate phosphatase (TMP phosphatase having EC 3.1.3.-) as well as transgenes encoding polypeptides that catalyze steps in the thiamine pathway. The genetically modified bacterium is characterized by enhanced synthesis and release of thiamine into the extracellular environment. The invention further provides a method for producing thiamine using the genetically modified bacterium of the invention; as well as the use of the genetically modified bacterium for extracellular thiamine production.

One or more genes in a biosynthesis pathway for a vitamin or other essential nutrient which is needed for the survival of a microorganism can be used as an effective selective marker to identify cells transformed with an exogenous nucleic acid. The microorganism does not naturally contain or express the one or more gene. This permits genetic manipulations to be performed. It permits lower cost fermentations to be performed. It permits production of the essential nutrient for subsequent commodity use.

One or more genes in a biosynthesis pathway for a vitamin or other essential nutrient which is needed for the survival of a microorganism can be used as an effective selective marker to identify cells transformed with an exogenous nucleic acid. The microorganism does not naturally contain or express the one or more gene. This permits genetic manipulations to be performed. It permits lower cost fermentations to be performed. It permits production of the essential nutrient for subsequent commodity use.

The present disclosure relates to a genetically modified host cell having improved production of thiamine, wherein the host cell expresses one or more heterologous ThiO enzymes converting glycine into dehydroglycine (DHG) in the host cell and/or one or more heterologous ThiI enzymes catalyzing the transfer of sulfur from IscS to the sulfur carrier protein ThiS in the host cell, whereby the production of the thiamine in the genetically modified host cell is improved compared to an unmodified parent host cell.