Transcriptional and Proteomic Responses ofPseudomonas aeruginosaPAO1 to Spaceflight Conditions Involve Hfq Regulation and Reveal a Role for Oxygen

Abstract

Assessing bacterial behavior in microgravity is important for risk assessment and prevention of infectious diseases during spaceflight missions. Furthermore, this research field allows the unveiling of novel connections between low-fluid-shear regions encountered by pathogens during their natural infection process and bacterial virulence. This study is the first to characterize the spaceflight-induced global transcriptional and proteomic responses of Pseudomonas aeruginosa, an opportunistic pathogen that is present in the space habitat. P. aeruginosa responded to spaceflight conditions through differential regulation of 167 genes and 28 proteins, with Hfq as a global transcriptional regulator. Since Hfq was also differentially regulated in spaceflight-grown Salmonella enterica serovar Typhimurium, Hfq represents the first spaceflight-induced regulator acting across bacterial species. The major P. aeruginosa virulence-related genes induced in spaceflight were the lecA and lecB lectin genes and the gene for rhamnosyltransferase (rhlA), which is involved in rhamnolipid production. The transcriptional response of spaceflight-grown P. aeruginosa was compared with our previous data for this organism grown in microgravity analogue conditions using the rotating wall vessel (RWV) bioreactor. Interesting similarities were observed, including, among others, similarities with regard to Hfq regulation and oxygen metabolism. While RWV-grown P. aeruginosa mainly induced genes involved in microaerophilic metabolism, P. aeruginosa cultured in spaceflight presumably adopted an anaerobic mode of growth, in which denitrification was most prominent. Whether the observed changes in pathogenesis-related gene expression in response to spaceflight culture could lead to an alteration of virulence in P. aeruginosa remains to be determined and will be important for infectious disease risk assessment and prevention, both during spaceflight missions and for the general public.The microgravity environment associated with spaceflight is unique and has a profound effect on both host and pathogen cells, with potential implications for infectious disease. From the host point of view, astronauts experience a compromised immune response under spaceflight conditions, as reflected in cellular alterations of both the innate and adaptive immune systems (23,26,40). Spaceflight has been shown to alter the response of monocytes, isolated from astronauts preflight and in flight, to . Further, simulation of aspects of this microgravity-associated decreased immune response, using the hind limb unloaded mouse model, showed an enhanced susceptibility of these animals to bacterial infection (3,6). From the pathogen's perspective, bacterial obligate and opportunistic pathogens have been found to exhibit enhanced stress resistance phenotypes following growth under both true spaceflight and microgravity analogue conditions (13,30,33,(46)(47)(48)(49). In response to the spaceflight environment, global transcriptional and proteomic changes were observed for the ente...

The Effects of Modeled Microgravity on Growth Kinetics, Antibiotic Susceptibility, Cold Growth, and the Virulence Potential of aYersinia pestis ymoA-Deficient Mutant and Its Isogenic Parental Strain

“…In addition to S. Typhimurium, enterotoxigenic and enteropathogenic E. coli (Chopra et al, 2006), adherent-invasive E. coli (Allen et al, 2008), and P. aeruginosa (Crabbé et al, 2008(Crabbé et al, , 2011 have also been characterized following CR growth. Interestingly, all the aforementioned pathogens responded to CR growth by similarly exhibiting enhanced virulence potentials.…”

“…In addition to S. Typhimurium, different strains of E. coli (Chopra et al, 2006;Allen et al, 2008) and P. aeruginosa (Crabbé et al, 2008(Crabbé et al, , 2011) also exhibited a hypervirulence phenotype or an enhanced virulence potential following CR. Our previous CR-related YP studies were the first published exception to the hypervirulence trend of CR-exposed Gramnegative pathogens .…”

Microbiological Lessons Learned From the Space Shuttle

“…Biodegradation of critical materials can result in system failures that may endanger crews. Evidence gained during the SSP suggests that infectious diseases and allergic responses may increase on long exploration missions due to sustained immune deficiencies (11)(12)(13)(14)(15) and increased virulence of some microorganism (7)(8)(9)(10). …”

“…To gain insight into this hypothesis, Nickerson et al (7,8) performed experiments aboard STS-115 and STS-123, operationally designated MICROBE and MDRV, in which the virulence, morphological characteristic, and molecular genetic responses of Salmonella enteric serovar Typhimurium (S. Typhimurium) during flight were compared to identically grown cultures on the ground. Microscopic analysis of the spaceflight grown S. Typhimurium from STS-115 indicated the presence of an extracellular matrix not seen in the ground grown controls, suggesting the potential of enhanced biofilm formation by the spaceflight cultures.…”

“…Our understanding of the effects of spaceflight on these life forms was greatly enhanced during the Space Shuttle Program (SSP). Some bacteria and fungi were shown to be more virulent as a result of spaceflight (7)(8)(9)(10). Immune studies showed decreases in innate immunity, cell mediated immunity (11)(12)(13)(14)(15), and increased latent virus reactivation (16)(17)(18)(19).…”