FIG 2.

Phenotypic differences of M. avium subsp. paratuberculosis strains following exposure to stress environments. Disc diffusion assays were carried out with M. avium subsp. paratuberculosis, M. avium subsp. paratuberculosis ΔsigL, and M. avium subsp. paratuberculosis ΔsigL::sigL strains with various concentrations of diamide (A) and SDS (B). Halos indicate that M. avium subsp. paratuberculosis ΔsigL is susceptible to both the thiol-specific oxidant diamide and cell envelope stress. Images are representative of two biological replicates. (C) Sustained effect of exposure to acidified bovine bile on M. avium subsp. paratuberculosis survival. The wild type, M. avium subsp. paratuberculosis ΔsigL, and complemented strains were cultured in the presence of 0.3% acidified bile, and CFU counts were determined at 0, 4, 15, 24, 48, and 72 h postexposure via plating on 7H10 medium. The growth difference between M. avium subsp. paratuberculosis ΔsigL mutant and the wild-type strain or complemented strain was statistically significant (*, P < 0.05) at all time points following exposure to acidified bile. Error bars represent the standard deviations.