Genetically-modified bacteria and uses thereof

A genetically-modified bacterium, for example of the class Actinobacteria, and the use of such a bacterium in the bioconversion of a steroidal substrate into a steroidal product of interest. A method of converting a steroidal substrate into a steroidal product of interest, wherein the method comprises: inoculating culture medium with genetically-modified bacteria according to any of Claims 1 to 28 and growing the bacterial culture until a target OD600 is reached; adding a steroidal substrate to the bacterial culture when the target OD600 is reached; culturing the bacterial culture so that the steroidal substrate is converted to the steroidal product of interest; and extracting and/or purifying the steroidal product of interest from the bacterial culture.