FIGURE 6.

Effects of stringent response on in vivo virulence and colonization. A, infant mice (n = 6) were infected with 50 μl of each V. cholerae strain (2 × 10⁶ cells) suspended in LB supplemented with 100 mm TMAO. After 24 h, mice were sacrificed, and the entire intestines were extracted for weight measurement. Mice that died prior to the planned time of sacrifice were used for the measurement right after death. The fluid accumulation ratio was calculated as described under “Experimental Procedures.” Values of means ± S.D. (error bars) are displayed in each bar. *, p < 0.05; **, p < 0.01 versus fluid accumulation ratio from infection with N16961. B, survival rate of mice infected with the indicated strains (2 × 10⁶ cells) was monitored every 3 h. The percentage survival in each group was plotted as Kaplan-Meier curves. C, mice were infected with the indicated bacterial strains (2 × 10⁶ cells) suspended in LB supplemented with 100 mm TMAO, and intestinal colonization was measured after 16 h by counting the number of viable bacterial cells recovered from the mouse intestine. The solid horizontal lines represent the geometric mean values. *, p < 0.001; **, p < 0.002 versus cfu from infection with wild type N16961. Each symbol shows the value obtained from each mouse.