A method is provided for identifying mycobacterial genes that are induced or up-regulated under continuous culture conditions defined by a dissolved oxygen tension of up to 10% air saturation measured at 37.degree. C. when compared with a dissolved oxygen tension of at least 40% air saturation measured at 37.degree. C. Said induced or up-regulated genes form the basis of nucleic acid vaccines, or provide targets to allow preparation of attenuated mycobacteria for vaccines against mycobacterial infections. Similarly, peptides encoded by said induced or up-regulated genes are employed in vaccines. In a further embodiment, the identified genes/peptides provide the means for identifying the presence of a mycobacterial infection in a clinical sample by nucleic acid probe or antibody detection.