Microbial stress: Spaceflight-induced alterations in microbial virulence and infectious disease risks for the crew

The response of microorganisms to the spaceflight environment has tremendous implications for the risk of infectious disease for astronauts. Seminal studies using Salmonella enterica serovar Typhimurium demonstrated that the organism's virulence was altered in response to culture in either spaceflight or spaceflight analogue environments. Furthermore, evaluation of global changes in transcriptomic and proteomic profiles in S. Typhimurium in response to culture in these environments indicated that many of the alterations in gene expression were regulated by the conserved chaperone protein, Hfq. To determine similarities in spaceflight and/or spaceflight analogue-induced responses in other pathogens, extensive studies were performed using the opportunistic pathogen Pseudomonas aeruginosa. As with S. Typhimurium, P. aeruginosa cultured in either spaceflight or spaceflight analogue conditions demonstrated diverse molecular genetic response profiles, including those associated with pathogenesis-related responses and the Hfq regulon. Collectively, these discoveries are providing novel insight into both the conserved and varied molecular genetic and phenotypic responses found in a wide variety of pathogens cultured in both spaceflight and spaceflight analogue conditions. Interestingly, the low fluid-shear culture conditions of both spaceflight and spaceflight analogue environments are relevant to those encountered by pathogens in certain regions of the human body during the natural course of infection. Hence, novel virulence strategies unveiled during spaceflight and spaceflight analogue culture hold promise to safeguard crew health, and may aid the quest for novel therapeutics and vaccines against pathogens for the general public on Earth.