Abstract: Polynucleotides associated with virulence in mycobacteria, and particularly a fragment of DNA isolated from M. bovis that contains a region encoding a putative sigma factor. Also provided are methods for a DNA sequence or sequences associated with virulence determinants in mycobacteria, and particularly in M. tuberculosis and M. bovis. The invention also provides corresponding polynucleotides associated with avirulence in mycobacteria. In addition, the invention provides a method for producing strains with altered virulence or other properties which can themselves be used to identify and manipulate individual genes.

Abstract: The embodiments of the invention are based upon the identification and characterization of genes that determine mycobacterial resistance to the antibiotic isoniazid (INH) and its analogs. These genes, termed inhA, encode a polypeptide, InhA, that is the target of action of mycobacteria for isoniazid. The sequences of wild-type INH-sensitive as well as allelic or mutant INH-resistant inhA genes and their operons are provided. Also provided are isolated InhA polypeptides of both the INH-resistant and INH-sensitive types.