The genetics of mycobacteria has lagged behind because of several reasons.
Mycobacteria grow very slowly. their generation time ranging anywhere between 12-24
hrs. Mycobacteria are rather hydrophobic and tend to grow in clusters and there is
difficulty in purifying individual cells for genetic analysis. Very few genetic markers have
been found in mycobacteria because there is no known naturally occurring genetic
exchange in mycobacteria. With the creation of genomic libraries of M. tuberculosis more
than 50 genes have been characterised. Many of them are not expressed efficiently in
Escherichia coli (E.coli) under the control of their own promoters, since very few
mycobacterial promoters are recognised by the E. coli transcription machinery. This clearly
shows that mycobacteria use a different system of gene regulation. Understanding the gene
regulation of mycobacteria might throw light on the slow growth rate, about their
persistence in a resting phase and also about their intracellular survival. Besides this if
inducible or strong promoters are identified they can be used in over expression of genes
coding for proteins useful in diagnosis and protection
