Response of Pseudomonas aeruginosa to spaceflight and spaceflight analogue culture: Implications for astronaut health and the clinic

Since its first reported isolation from an astronaut in 1970, the opportunistic pathogen Pseudomonas aeruginosa has been a commonly studied microorganism in microgravity and microgravity-analogue conditions. Besides being part of the normal human flora, P. aeruginosa is ubiquitous in the crew’s direct surroundings, including air, water, and surfaces. This chapter describes the main results from the phenotypic and molecular genetic responses of this clinically important bacterium to the spaceflight environment. Culturing P. aeruginosa in microgravity and/or microgravity-analogue conditions gave rise to an altered biofilm phenotype, increased resistance to environmental stressors and certain antibiotics, enhanced production of virulence factors, and differential gene expression. The RNA-binding protein Hfq was identified as a potential key transcriptional regulator in the microgravity and microgravity-analogue responses of P. aeruginosa, which suggests a conserved response with Salmonella enterica serovar Typhimurium (the first pathogen for which this response was observed in both microgravity and microgravity-analogue culture) and Staphylococcus aureus. Besides the importance of these findings for the risk assessment, prevention, and treatment of infectious diseases during short-term and long-duration spaceflight missions, they entail applications for the clinic. Specifically, the low fluid-shear conditions encountered in microgravity-analogue (and potentially microgravity) conditions are relevant to the microenvironment encountered by P. aeruginosa during mucosal infections, including in the lungs of cystic fibrosis patients. Further research is needed to evaluate whether the altered behavior of P. aeruginosa in microgravity conditions in combination with the immunocompromised nature of astronauts could lead to a higher risk for infectious diseases. In addition, expanding our knowledge on how the in vivo microenvironmental conditions, including low fluid-shear, affect the disease phenotype of P. aeruginosa could help in the design of novel strategies to prevent and combat this opportunistic pathogen both during spaceflight missions and in the clinic.