Phenotypic characterization of a novel double knockout PknI/DacB2 from Mycobacterium tuberculosis.

Serine/threonine protein kinases play a major role in peptidoglycan biosynthesis in Mycobacterium tuberculosis. To explore the mechanism in detail, in the present study, we have constructed a double knockout (DKO) strain lacking pknI and dacB2 in M. tuberculosis. Initially, we analyzed the colony morphology and found that the DKO strain showed smoother colony morphology on solid agar and irregular shape in transmission electron microscopy. In addition, the DKO strain exhibits defective biofilm and cord formation. The DKO strain was found to be hypersensitive to cell wall damaging agents such as lysozyme, malachite green, ethidium bromide and to isoniazid, a first line anti-TB drug. In conclusion, our data suggest that both pknI and dacB2 play an important role in the maintenance of colony morphology, cell wall permeability and integrity of M. tuberculosis.