The cost of bacterial predation via type VI secretion system leads to predator extinction under environmental stress
- Campylobacter jejuni uses Type VI secretion system (T6SS) to kill prey bacteria
- Under bile salt stress, activated T6SS may promote bile salt uptake and DNA damage
- T6SS-dependent predation by C. jejuni thus entails a “predation cost” under stress
- The predation cost leads to predator extinction and host defense against C. jejuni
As a common gut pathogen, Campylobacter jejuni (C. jejuni) harbors the Type VI Secretion System (T6SS) that injects toxic effectors into neighboring cells, modulating microbial competitions in the harsh gut environment. Using bile salt as a natural stressor and T6SS-positive C. jejuni as a predator, we show that T6SS activity could entail a cost during bacterial predation under environmental stress. Our data suggest bile salt influx and subsequent DNA damage due to the prey-driven activation of the T6SS. We further combined experiments and mathematical modeling to explore how the stress-induced “predation cost” determines ecological outcomes. Consistent with a population-dynamics model, we found predator extinction above a critical bile salt concentration and prey-predator coexistence below this level. Moreover, we utilized the predation cost as an effective strategy facilitating host defense against C. jejuni infection. Together, we elucidate how predator dominance versus extinction emerges from the interplay between environmental stress and the T6SS machinery.