Fig. 4.

Effects of exogenous addition of cyclic dipeptides on the survival of B. vulgatus. A, B, and C Effect of cyclo-Phe-Pro (cFP) on the survival of the strains of B. vulgatus. Various concentrations of cFP ranging from 0 to 1.0 mM were added to the freshly grown cultures of three strains of B. vulgatus in M9 broth: MGM001 (A), ATCC8482 (B), and DSM28735 (C). At 6 h post-exposure to cFP, B. vulgatus CFUs were enumerated as described in Fig. 2C. The P-values for the comparison with the control (0 mM cFP) are indicated (Student’s t-test; ns, not significant; *0.001 < P < 0.01; **P < 0.001). D Effects of Phe (F), Pro (P), and a dipeptide of Phe-Pro (F-P) on the survival of B. vulgatus. Various concentrations of F, P, and F-P ranging from 0 to 1.0 mM were added to the freshly grown culture of B. vulgatus MGM001. At 6 h post-exposure, B. vulgatus CFUs were enumerated as described in Fig. 2C. E Effects of other cyclic dipeptides on the survival of B. vulgatus. Various concentrations of cyclo-Phe-Val (cPV) and cyclo-Pro-Thr (cPT) ranging from 0 to 4.0 mM were added to the freshly grown culture of B. vulgatus MGM001. At 6 h post-exposure, B. vulgatus CFUs were enumerated as described in Fig. 2C