Transcriptional and Proteomic Responses of Pseudomonas aeruginosa PAO1 to Spaceflight Conditions Involve Hfq Regulation and Reveal a Role for Oxygen

The Biodesign Institute, Center for Infectious Diseases and Vaccinology, Arizona State University, 1001 S. McAllister Avenue, Tempe, AZ 85287, UDA.
Applied and Environmental Microbiology (Impact Factor: 3.67). 02/2011; 77(4):1221-30. DOI: 10.1128/AEM.01582-10
Source: PubMed


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.

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    • "The RWV culture apparatus (Fig. 1) allows a physiolo-gically-relevant low fluid shear force growth environment that induces a number of phenotypic responses in bacteria including altered stress resistance [1-5, 7, 12, 16, 21], increased survival in cellular and animal hosts [1, 3, 4, 7], and altered gene expression [1, 3, 5, 7, 13, 14, 17, 18]. The RWV is used to induce prokaryotic and eukaryotic cellular phenotypes that are difficult or not possible to obtain using conventional culture conditions [1, 18, 21, 24]. "
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    ABSTRACT: Low fluid shear force, including that encountered in microgravity models, induces bacterial responses, but the range of bacteria capable of responding to this signal remains poorly characterized. We systematically analyzed a range of Gram negative Enterobacteriaceae for conservation of the low-shear modeled microgravity (LSMMG) response using phenotypic assays, qPCR, and targeted mutations. Our results indicate LSMMG response conservation across Enterobacteriacae with potential variance in up- or down-regulation of a given response depending on genus. Based on the data, we analyzed the role of the trp operon genes and the TrpR regulator in the LSMMG response using targeted mutations in these genes in S. Typhimurium and E. coli. We found no alteration of the LSMMG response compared to WT in these mutant strains under the conditions tested here. To our knowledge, this study is first-of-kind for Citrobacter, Enterobacter, and Serratia, presents novel data for Escherichia, and provides the first analysis of trp genes in LSMMG responses. This impacts our understanding of how LSMMG affects bacteria and our ability to modify bacteria with this condition in the future.
    The Open Microbiology Journal 06/2014; 8(1):51-8. DOI:10.2174/1874285801408010051
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    • "To study P. aeruginosa biofilm formation during spaceflight, we used specialized hardware designed for growing cells during spaceflight, known as a fluid processing apparatus (FPA; Figure S1). FPAs have been used in several recent studies of bacterial growth and physiology during spaceflight [11], [16], [17]. Briefly, an FPA is a glass barrel that can be divided into compartments by rubber stoppers. "
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    ABSTRACT: Understanding the effects of spaceflight on microbial communities is crucial for the success of long-term, manned space missions. Surface-associated bacterial communities, known as biofilms, were abundant on the Mir space station and continue to be a challenge on the International Space Station. The health and safety hazards linked to the development of biofilms are of particular concern due to the suppression of immune function observed during spaceflight. While planktonic cultures of microbes have indicated that spaceflight can lead to increases in growth and virulence, the effects of spaceflight on biofilm development and physiology remain unclear. To address this issue, Pseudomonas aeruginosa was cultured during two Space Shuttle Atlantis missions: STS-132 and STS-135, and the biofilms formed during spaceflight were characterized. Spaceflight was observed to increase the number of viable cells, biofilm biomass, and thickness relative to normal gravity controls. Moreover, the biofilms formed during spaceflight exhibited a column-and-canopy structure that has not been observed on Earth. The increase in the amount of biofilms and the formation of the novel architecture during spaceflight were observed to be independent of carbon source and phosphate concentrations in the media. However, flagella-driven motility was shown to be essential for the formation of this biofilm architecture during spaceflight. These findings represent the first evidence that spaceflight affects community-level behaviors of bacteria and highlight the importance of understanding how both harmful and beneficial human-microbe interactions may be altered during spaceflight.
    PLoS ONE 04/2013; 8(4):e62437. DOI:10.1371/journal.pone.0062437 · 3.23 Impact Factor
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    • "Taking into consideration that the Hfq regulon is differentially expressed in both P. aeruginosa (Crabbé et al., 2011) and S. Typhimurium (Wilson et al., 2007) following space-flight strongly suggests that Hfq is a space-responsive gene necessary for rapid bacterial re-programming in the aforementioned environment . Interestingly, when Staphylococcus aureus was grown under SMG conditions, it also exhibited down-regulated expression of hfq (Castro et al., 2011) in a manner consistent with what was formerly observed in P. aeruginosa and S. Typhymirium (Wilson et al., 2007; Crabbé et al., 2011). However, unlike the two aforementioned bacterial species, the S. aureus response to SMG resulted in decreased virulence potential (Castro et al., 2011). "
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    ABSTRACT: Manned space exploration has created a need to evaluate the effects of space-like stress (SLS) on pathogenic and opportunistic microbes. Interestingly, several Gram-negative enteric pathogens, e.g., Salmonella enterica serovar Typhimurium, have revealed a transient hyper-virulent phenotype following simulated microgravity (SMG) or actual space flight exposures. We have explored the virulence potential of Yersinia pestis KIM/D27 (YP) following exposure to mechanical low shear forces associated with SMG. Our experimental results demonstrated that SMG-grown YP was decreased in its induced HeLa cell cytotoxicity, suggesting that SMG somehow compromises T3SS functions. This was confirmed by an actual reduced amount of effector protein production and secretion through the T3SS injectisome. Also, SMG-grown YP proliferated less than their NG-grown counterparts did during an 8-h macrophage infection. Presently, we are evaluating the influence of SMG on various KIM/D27 mutant strains to further understanding of our initial phenomenology described above. Taken together, characterizing YP grown under the low shear forces of SMG can provide new insights into its pathogenesis and potentially uncover new targets that could be exploited for the development of novel antimicrobials as well as potential live-attenuated vaccines.
    Frontiers in Cellular and Infection Microbiology 08/2012; 2:107. DOI:10.3389/fcimb.2012.00107 · 3.72 Impact Factor
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