Observed versus predicted colony counts for H37Rv strain at log phase (A1 and A2) and acid phase (B1 and B2), for 18b strain at log phase (C1 and C2), NRP phase in sn acidic pH environment (D1 and D2), and NRP phase in a neutral pH environment (E1 and E2). 1 and 2 are replicates for the same experiment. Red lines represent the regression lines over the observed versus model predicted colony counts, the black lines represent the unity lines; ●, observation/prediction pairs.