The present invention relates to methods and compositions for reducing the risk and severity of C. difficile infection. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacterium Clostridium scindens, contributes substantially to resistance against C. difficile infection. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids.

The present invention relates to a coupled biotransformation process of converting chenodeoxycholic acid (CDCA) and related compounds to ursodeoxycholic acid (UDCA) and related compounds. It also relates to the cloning, expression, and biochemical characterization of a novel NADP.sup.+-dependent 7α-hydroxysteroid dehydrogenase (7α-HSDH) from Clostridium difficile, cofactor switch mutants thereof, and their application for the oxidation of bile acids. A further aspect of the invention relates to novel NADP-dependent cofactor switch mutants of the NADP.sup.+-dependent 7α-HSDH of E. coli and their application for the oxidation of bile acids.

The present invention relates to methods and compositions for reducing the risk and severity of C. difficile infection. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacterium Clostridium scindens, contributes substantially to resistance against C. difficile infection. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids.

The invention relates to novel 3-hydroxysteroid dehydrogenase mutants, to the sequences which code for these enzyme mutants, to processes for the preparation of the enzyme mutants and to their use in enzymatic conversions of cholic acid compounds, in particular in the preparation of ursodeoxycholic acid (UDCA); subject-matter of the invention is also novel processes for the synthesis of UDCA using enzyme mutants; and the preparation of UDCA using recombinant, multiply modified microorganisms.

The invention provides novel 3α-hydroxysteroid dehydrogenase mutants, sequences that code for these enzyme mutants, methods for producing the enzyme mutants, and the use thereof in enzymatic reactions of cholic acid compounds, and in particular in the production of ursodeoxycholic acid (UDCA). The invention further provides processes for the synthesis of UDCA using the enzyme mutants and the production of UDCA using recombinant microorganisms that have been subjected to multiple modifications.

Genetically-modified cell capable of producing UD CA, cholic acid, and/or another UDCA precursor comprising at least one heterologous polynucleotide encoding an enzyme involved in a metabolic pathway that converts sugar to UDCA, cholic acid, and/or another UDCA precursor. Method of making UDCA, cholic acid, and/or another UDCA precursor using such a cell. Use of UDCA or UDCA precursor produced using such a method for the manufacture of a medicament for the treatment of a disease or symptom of a disease. Medicament comprising UDCA or UDCA precursor made using such a method. Method of treating a disease or symptom of a disease comprising administering UDCA or a UDCA precursor made using such a method. Isolated nucleic acid encoding at least one enzyme involved in a metabolic pathway that converts sugar to UDCA, cholic acid, and/or another UDCA precursor. Vector comprising a nucleic acid encoding at least one enzyme involved in a metabolic pathway that converts sugar to UDCA, cholic acid and/or another UDCA precursor. Method of making a genetically-modified cell capable of synthesizing UDCA, cholic acid, and/or another UDCA precursor. Composition comprising UDCA or a UDCA precursor, a free acid or CoA thereof, or a pharmaceutically-acceptable derivative or prodrug thereof.

The present invention relates to a coupled biotransformation process of converting chenodeoxycholic acid (CDCA) and related compounds to ursodeoxycholic acid (UDCA) and related compounds. It also relates to the cloning, expression, and biochemical characterization of a novel NADP.sup.+-dependent 7-hydroxysteroid dehydrogenase (7-HSDH) from Clostridium difficile, cofactor switch mutants thereof, and their application for the oxidation of bile acids. A further aspect of the invention relates to novel NADP-dependent cofactor switch mutants of the NADP.sup.+-dependent 7-HSDH of E. coli and their application for the oxidation of bile acids.

The invention provides novel 3-hydroxysteroid dehydrogenase mutants, sequences that code for these enzyme mutants, methods for producing the enzyme mutants, and o the use thereof in enzymatic reactions of cholic acid compounds, and in particular in the production of ursodeoxycholic acid (UDCA). The invention further provides processes for the synthesis of UDCA using the enzyme mutants and the production of UDCA using recombinant microorganisms that have been subjected to multiple modifications.

The present invention relates to methods and compositions for reducing the risk and severity of C. difficile infection. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacterium Clostridium scindens, contributes substantially to resistance against C. difficile infection. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids.

The present invention relates to methods and compositions for reducing the risk and severity of C. difficile infection. It is based, at least in part, on the discovery that a restricted fraction of the gut microbiota, including the bacterium Clostridium scindens, contributes substantially to resistance against C. difficile infection. Without being bound by any particular theory, it is believed that this is achieved through the biosynthesis of secondary bile acids.