Combined Effects of Microgravity Analogue Culture and Incremental Oxygen Levels on Bacterial Pathogen Adaptive Responses

Project: Research project

Description

Project Summary Our collaborative research team and others have shown that spaceflight and/or spaceflight-analogue culture leads to global alterations in the virulence, gene expression and/or pathogenesis-related phenotypes of a broad spectrum of pathogens, including Salmonella enterica serovar Typhimurium (S. Typhimurium), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans). We have also demonstrated that common molecular strategies are shared between all of the afore-mentioned pathogens in regulating their pathogenic response to spaceflight and/or spaceflight analogue culture. In combination with spaceflight-induced alterations in crew immune function, these data suggest an increased risk of infectious disease during spaceflight missions. While changes in microbial responses to the spaceflight environment and corresponding risk to crew health are well-documented, the environmental stimulus/stimuli are unclear. The mechanisms behind the environmental stimulus have been speculated to derive from changes in environmental factors, such as mass transfer and fluid shear. Indeed, our previous microgravity and microgravity-analogue studies indicate that the observed alterations in microbial virulence and/or pathogenesis-related characteristics may be stimulated by possible secondary/indirect environmental effects during culture in these environments, including fluid shear and decreased mass transfer of nutrients and oxygen. Our results evaluating gene expression and pathogenic stress responses in P. aeruginosa and S. aureus cultured in spaceflight and/or the spaceflight analogue, Rotating Wall Vessel (RWV) bioreactor, suggest that a limited transfer rate of oxygen may be a factor that induces or exacerbates the microbial response to this environment. The RWV bioreactor was developed to produce a low-fluid shear, low-turbulence environment for suspension culture (that we have termed low shear modeled microgravity/LSMMG) that models aspects of spaceflight. We have shown that microbial responses observed using this analogue have been predictive of bacterial responses obtained from true spaceflight, thus the RWV was chosen as the spaceflight-analogue culture system for this study. Based upon our collective findings, we speculate that limited oxygen transfer may contribute to the altered microbial characteristics in the low fluid shear environments of true spaceflight and the RWV bioreactor. We thus hypothesize that the combined effect of LSMMG culture and incremental oxygen levels will alter pathogenesisrelated stress responses and gene expression of S. Typhimurium and unveil novel connections between these environments in a way that neither approach alone or conventional culture could achieve. Our previous microgravity and RWV studies have been performed without modulation of oxygen levels, therefore the impact of oxygen on experimental outcomes is not clear. Like many pathogens, Salmonella naturally encounters a wide range of oxygen concentrations in the infected host and in environmental reservoirs. Indeed, as a facultative anaerobe, Salmonella thrives in environments ranging from anaerobicmicroaerophilic- aerobic conditions. Since oxygen is known to regulate Salmonella gene expression, pathogenesis-related stress responses (including acid stress, oxidative stress, macrophage survival and invasion) and virulence), and since LSMMG culture also regulates the majority of these same responses, it is logical to examine the association between LSMMG-induced responses in the context of different controlled oxygen levels. However, no studies have been done to examine the direct role of oxygen in the microbial LSMMG response and its potential to alter gene expression and pathogenic responses of bacteria to a microgravity analogue environment.
StatusFinished
Effective start/end date2/1/158/31/16

Funding

  • NASA: Johnson Space Center: $95,784.00

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Weightlessness
Space Flight
Oxygen
Gene Expression
Bioreactors
Salmonella
Virulence
Pseudomonas aeruginosa
Staphylococcus aureus
Salmonella enterica
Candida albicans
Communicable Diseases
Suspensions