Figure 1B shows that both strains grow similarly in the lungs of C3HeB/FeJ mice after a low-dose aerosol infection. Using TK specific primers and colony PCR, the TK gene was reliably amplified from all the randomly picked M. tuberculosis Phsp60 TK colonies (n = 13) obtained from lung homogenates 8-weeks after aerosol infection (Figure 1C) but not from the negative control. This evidence concerns the gene TKT and infection.