Molecular cloning of mycobacterial promoters in Escherichia coli

Mycobacterium bovis BCG chromosomal DNA, digested with EcoR1 and HindIII, was used to construct a promoter library in Escherichia coli using the promoter probe plasmid pKO-1. DNA inserts of various sizes showed promoter activity judged by the level of galactokinase (galK) whose synthesis they activate (between 50 and 850 galactokinase units). No correlation between the length of the DNA insert and the level of the galactokinase was found suggesting that the multicopy pool of the promoters does not influence the level of the transcription of the galK gene.