Dataset Information

Exposure of Mycobacterium marinum to low-shear modeled microgravity: effect on growth, the transcriptome and survival under stress.

ABSTRACT: Waterborne pathogenic mycobacteria can form biofilms, and certain species can cause hard-to-treat human lung infections. Astronaut health could therefore be compromised if the spacecraft environment or water becomes contaminated with pathogenic mycobacteria. This work uses Mycobacterium marinum to determine the physiological changes in a pathogenic mycobacteria grown under low-shear modeled microgravity (LSMMG). M. marinum were grown in high aspect ratio vessels (HARVs) using a rotary cell culture system subjected to LSMMG or the control orientation (normal gravity, NG) and the cultures used to determine bacterial growth, bacterium size, transcriptome changes, and resistance to stress. Two exposure times to LSMMG and NG were examined: bacteria were grown for ~40?h (short), or 4 days followed by re-dilution and growth for ~35?h (long). M. marinum exposed to LSMMG transitioned from exponential phase earlier than the NG culture. They were more sensitive to hydrogen peroxide but showed no change in resistance to gamma radiation or pH 3.5. RNA-Seq detected significantly altered transcript levels for 562 and 328 genes under LSMMG after short and long exposure times, respectively. Results suggest that LSMMG induced a reduction in translation, a downregulation of metabolism, an increase in lipid degradation, and increased chaperone and mycobactin expression. Sigma factor H (sigH) was the only sigma factor transcript induced by LSMMG after both short and long exposure times. In summary, transcriptome studies suggest that LSMMG may simulate a nutrient-deprived environment similar to that found within macrophage during infection. SigH is also implicated in the M. marinum LSMMG transcriptome response.

SUBMITTER: Abshire CF

PROVIDER: S-EPMC5515531 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Exposure of Mycobacterium marinum to low-shear modeled microgravity: effect on growth, the transcriptome and survival under stress.

Abshire Camille F CF Prasai Kanchanjunga K Soto Israel I Shi Runhua R Concha Monica M Baddoo Melody M Flemington Erik K EK Ennis Don G DG Scott Rona S RS Harrison Lynn L

NPJ microgravity 20161201

Waterborne pathogenic mycobacteria can form biofilms, and certain species can cause hard-to-treat human lung infections. Astronaut health could therefore be compromised if the spacecraft environment or water becomes contaminated with pathogenic mycobacteria. This work uses Mycobacterium marinum to determine the physiological changes in a pathogenic mycobacteria grown under low-shear modeled microgravity (LSMMG). M. marinum were grown in high aspect ratio vessels (HARVs) using a rot ...[more]

PMID: 28725743

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Project description:Anticipating the risk for infectious disease during space exploration and habitation is a critical factor to ensure safety, health and performance of the crewmembers. As a ubiquitous environmental organism that is occasionally part of the human flora, Pseudomonas aeruginosa could pose a health hazard for the immuno-compromised astronauts. In order to gain insights in the behavior of P. aeruginosa in spaceflight conditions, two spaceflight-analogue culture systems, i.e. the rotating wall vessel (RWV) and the random position machine (RPM), were used. Microarray analysis of P. aeruginosa PAO1 grown in the low shear modeled microgravity (LSMMG) environment of the RWV compared to the normal gravity control (NG), revealed a regulatory role for AlgU (RpoE). Specifically, P. aeruginosa cultured in LSMMG exhibited increased alginate production and up-regulation of AlgU-controlled transcripts, including those encoding stress-related proteins. This study also shows the involvement of Hfq in the LSMMG response, consistent with its previously identified role in the Salmonella LSMMG- and spaceflight response. Furthermore, cultivation in LSMMG increased heat- and oxidative stress resistance and caused a decrease in the culture oxygen transfer rate. Interestingly, the global transcriptional response of P. aeruginosa grown in the RPM was similar to that in NG. The possible role of differences in fluid mixing between the RWV and RPM is discussed, with the overall collective data favoring the RWV as the optimal model to study the LSMMG-response of suspended cells. This study represents a first step towards the identification of specific virulence mechanisms of P. aeruginosa activated in response to spaceflight-analogue conditions, and could direct future research regarding the risk assessment and prevention of Pseudomonas infections for the crew in flight and the general public. The wild type P. aeruginosa PAO1 strain (ATCC 15692) was used in this study and all cultures were grown in Lennox L Broth Base (LB) (Life Technologies) at 28 Â°C. An overnight shaking culture (125 r.p.m.) of P. aeruginosa in LB was washed and diluted in 0.85% NaCl solution to an OD600 of 1. This bacterial suspension was used to inoculate fresh LB medium at a final concentration of 10-4 CFU/ml. Synthecon Rotating Wall Vessel bioreactors (RWV) (50 ml or 10 ml) were filled with inoculated medium so that no headspace (i.e. no bubbles) was present. Other than for stress resistance assays, for which 10 ml capacity bioreactors were used, RWV bioreactors with a capacity of 50 ml were adopted for all experiments. Identical bioreactors were mounted in triplicate on (i) a RWV device in vertical position (LSMMG) (Cellon), (ii) a RWV device in horizontal position (NG) and (iii) the center of the inner Random Positioning Machine (RPM) frame (RG) (Fokker Space), and placed in a large humidified (70%-80% relative humidity) culture chamber, to avoid evaporation of culture medium through the gas-permeable membrane at the back of each vessel (Figure 1). A 25 r.p.m. rotation speed was adopted for the RWV cultures, while RPM-cultures were randomly rotated at 10 r.p.m. (60Â°/s). Bacteria were grown in the three described test conditions for 24 hours. After 24 hours of cultivation, the contents of every bioreactor was gently mixed by pipetting and divided into several aliquots. Ten millilitres of culture from each growth condition was immediately fixed with RNA Protect Reagent (Qiagen), following the manufacturer's instructions, and fixed cell pellets were frozen at -20 Â°C until RNA extraction. Samples were immediately exposed to different stresses.

Dataset Information

Exposure of Mycobacterium marinum to low-shear modeled microgravity: effect on growth, the transcriptome and survival under stress.

Publications

Exposure of <i>Mycobacterium marinum</i> to low-shear modeled microgravity: effect on growth, the transcriptome and survival under stress.

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