Microgravity as a novel environmental signal affecting Salmonella entericaserovar Typhimurium virulence

The effects of spaceflight on the infectious disease process have only been studied at the level of the host immune response and indicate a blunting o f the immune mechanism in humans and animals. Accordingly, it is necessary to assess potential changes in microbial virulence associated with spacefli ght which may impact the probability of in-flight infectious disease. In th is study, we investigated the effect of altered gravitational vectors on Sa lmonella virulence in mice. Salmonella enterica serovar Typhimurium grown u nder modeled microgravity (MMG) were more virulent and were recovered in hi gher numbers from the murine spleen and liver following oral infection comp ared to organisms grown under normal gravity. Furthermore, MMG-grown salmon ellae were more resistant to acid stress and macrophage killing and exhibit ed significant differences in protein synthesis than did normal-gravity-gro wn cells. Our results indicate that the environment created by simulated mi crogravity represents a novel environmental regulatory factor of Salmonella virulence.