Hypermutation-induced in vivo oxidative stress resistance enhances Vibrio cholerae host adaptation
Fig 3
Recolonization and ROS resistance of passaged V. cholerae.
A. Competitive index of recolonized isolates. Twenty-four ΔmutS mutants isolated from NAC- mice were complemented by a chromosomal copy of mutS (ΔmutS*) into the lacZ locus. Five wildtype colonies were also selected (WT*) as a control. These isolates were co-infected with wildtype (lacZ+) into 6-week-old CD-1 NAC- and NAC+ mice. Fecal pellets were collected after 5 days and plated onto selective plates. The competitive index was calculated as the mutant to wildtype output ratio normalized to the input ratio. One-way ANOVA test P value < 0.001 includes WT* (NAC+/-) vs ΔmutS* (NAC-) and ΔmutS* (NAC-) vs ΔmutS* (NAC+). B. ROS resistance. Mid-log cultures of wildtype, ΔmutS, and in vivo-isolated wildtype (WT*), and ΔmutS (lacZ::mutS) (ΔmutS*) were diluted into saline and into saline containing 300 μM H2O2. After a 1 hr incubation, viable cells were enumerated. Survival rate was calculated by normalizing CFU to the H2O2-treated group. Error bars represent means and SDs from three independent experiments. C. Catalase production. Mid-log cultures were induced with 500 μM H2O2 for 1 hr. The lysates were then subjected to catalase activity assays. Error bars represent means and SDs from three independent experiments. Circles: smooth variants; squares: rugose colony variants.