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NASA NTRSDate not supplied

PLANNING FOR VEG-05 TOMATO CROP PRODUCTION ON THE INTERNATIONAL SPACE STATION

Growing fresh, nutritious, palatable produce for crew consumption during spaceflight may provide health-promoting, bioavailable nutrients and enhance the astronaut dietary experience as we move toward longer-duration missions. Tending plants may also serve as a countermeasure for crew psychological stresses associated with spaceflight. However, requirements to support consistent growth of a variety of nutritious crops under spaceflight environmental conditions remain unclear. This study explores the potential to grow crops for consumption on the International Space Station (ISS) using the Veggie vegetable-production system. Mizuna mustard was grown during VEG-04 studies in 2019, and human and plant data from those tests continue to be analyzed. Tomato plants will be grown for the VEG-05 experiment, and preflight definition studies are underway to ascertain the best hardware and operations for growing this fruiting crop. The variety of tomato selected for this study is ‘Red Robin’, a compact cherry tomato. Plants will be grown under two different red: blue lighting treatments using the Veggie units on ISS, and the impact of spectral quality on plant growth and yield, nutrient content, organoleptic acceptability, and microbial composition of the tomatoes will be assessed. Preliminary testing with this crop helped to identify responses to different analog types of growth hardware including both plant pillows and Passive Orbital Nutrient Delivery System (PONDS) units, and current testing is focusing on flight-like versions of this hardware. Challenges with fertilizer salts leaching out into the plant wicks and burning the stems of tomato were observed in earlier tests, so amended fertilizer and wick configurations have been developed. Crew procedures including plant thinning, watering, height adjustment with respect to lighting, and pollination are being validated. VEG-05 will be the first test of tomato fruit production on ISS. Lessons learned during preparation and implementation of the VEG-04 mizuna test for watering, and a separate ISS investigation with peppers (PH-04) in the Advanced Plant Habitat (APH) in terms of fertilizer, plant wicks, and pollination, will be adapted for this experiment. This research was co-funded by the Human Research Program and Space Biology (MTL#1075) in the ILSRA 2015 NRA call.

Veggie↗

NASA NTRSDate not supplied

Planning for VEG-05 Tomato Crop Production on the International Space Station

Veggie↗

NASA NTRS1993

Long-term productivity in the cryptoendolithic microbial community of the Ross Desert, Antarctica

Annual gross productivity of the lichen-dominated cryptoendolithic community was calculated from a computer analysis of photosynthetic response based on laboratory measurements of CO2 exchange and three years (1985-1988) of field nanoclimate data. Photosynthetic optimum increased from -3 to 2 degrees C between irradiance levels of 100 and 1500 micromoles photons m-2 s-1, while the upper compensation point rose from 1 to 17 degrees C. The mean yearly total time available for metabolic activity (temperature above -10 degrees C and moisture present) was 771.3 h for horizontal rock, 421.5 h for northeast-oriented sloped rock, and 1042.2 h for a small depression in horizontal rock (the characteristic site of occasional lichen apothecia). The calculated mean gross productivity value for a horizontal rock was 1215 mg C m-2 y-1, and net photosynthetic gain was 606 mg C m-2 y-1. Net ecosystem productivity (annual accretion of cellular biomass) estimated from long-term events amounted to only about 3 mg C m-2 y-1. The difference between these two values may represent the long-term metabolic costs of the frequent dehydration-rehydration and freezing-thawing cycles or of overwintering, and may account for the leaching of organic substances to the rock. The yearly gross productivity of the cryptoendolithic microbial community of the entire Ross Desert area was estimated at approximately 120,000-180,000 kg C. Of this, 600-900 kg C is in microbial biomass, and much of the rest is soluble compounds that leach into the rocks and possibly percolate to the valleys, providing a source of organic matter for lakes, rivers, and soils.

NASA Program Exobiology↗

NASA NTRS2011

Parabolic Flight Evaluation of Bacterial Adhesion on Multiple Antimicrobial Surface Treatments

This report describes the development of a test method and the evaluation of the effectiveness of antimicrobial technologies in reduced gravity based on parabolic flight experiments. Microbial growth is a common occurrence on fully immersed wetted surfaces in spacecraft environmental control and life support systems despite the use of chemical and/or physical \disinfection. Many materials and surface treatments with antimicrobial properties are commercially available but none have been vetted for spaceflight applications. Herein a test method is explained that included ground and reduced gravity parabolic flight experiments with a standard microorganism recovered from spacecraft, Pseudomonas aeruginosa, added at a concentration of 1 x 10(exp 5) cells per milliliter (mL) onto challenge material coupon surfaces. Several experimental materials were observed to slightly reduce microbial attachment in reduced gravity flight experiments, but none were capable of eliminating all challenge bacteria. Lunar gravity had an increased antimicrobial effect in 28 out of 36 test coupons compared to microgravity when provided otherwise identical conditions for growth, suggesting trace .amounts of gravity may be required for maximum antimicrobial performance. Bacterial cells exposed to variable gravity had more than twice as ,much intracellular adenosine triphosphate (ATP) when compared to control cells exposed only to Earth gravity due to a short duration response to environmental stress. An ATP luminescence assay was the method most amenable to development of an in-flight microbial monitoring assay

Birmele, Michele↗

NASA NTRSDate not supplied

Lessons from Earth Aerobiology for Venus Astrobiology

Venus’s clouds have often suggested as a possible habitat. The constraints governing putative airborne life in such a habitat in turn inform priorities and strategies for remote and in situ exploration, methods by which resulting biosignatures might be detected, exoplanet habitability assessment, and planetary protection concerns. Lessons drawn from studying Earth’s aerobiosphere can help improve this understanding. There are altitude ranges within Venus’s clouds in which temperature, pressure, particle size, and radiation appear to be within the limits of microbial life on Earth, and life cycles involving S- and Fe-based redox metabolism have been proposed. However, given the lack of a habitable surface reservoir, a long-term stable Venus aerobiosphere would require that the reproduction rate of the airborne microbes be faster than the settling rate of airborne microbes due to gravity, or eventually the population would be depleted; put another way, the mean generation time would need to exceed the mean residence time. This creates a joint constraint of aerosol dynamics, potential nutrient availability and energy influx, and bioenergetic costs such as desiccation and radiation damage. Even at an optimistic estimate of 75% H2SO4, Venus aerosol water activity (aw) is still ~0.02, far below the observed microbial growth limit of ~0.6. Long-term desiccation with brief spurts of repair and growth in response to transient water influx, such as from volcanism, is the most likely model for Earth-like life on Venus – a ‘desert bloom’ scenario. Several high-priority science goals – cloud aerosol composition, internal radiative flux, and aerosol residence time and circulation models – thus will also improve our understanding of Venus in an astrobiology context. In Earth’s troposphere, warm water clouds can carry 103 – 105 cells/mL, some metabolically active. However, Earth’s stratospheric sulfate aerosol layer may be a better analogue: supercooled sulfuric acidaerosols (acid weight fraction 0.6 – 0.85, 0.1 – 1 μm diameter, 0.1 – 1 cm-3) with little water activity, long residence times, high UV radiation, and only sporadic influx from surface particle sources. Though ‘hot spots’ can occur associated with tropospheric mixing, viable cells in stratospheric samples are rare (~102 cells/m3), and primarily inactive forms such as spores. It is not yet clear whether such bioaerosols are associated with sulfate aerosols or simply co-located, and reproduction in situ has not yet been observed. In this model of a sparse, largely dormant Venus ecosystem, a single transect on descent is likely to pass through a low-water, inactive region, missing potential signs of habitability or biosignatures. A targeted strategy would sample through an aerial region with some upwelling from surface sources, andtake multiple transects separated in time and space. This is compatible with other in situ science goals seeking to understand the dynamics and heterogeneities of Venus’s clouds.

Lower atmosphere↗

NASA NTRS2000

Controlling Microbial Byproducts using Model-Based Substrate Monitoring and Control Strategies

We have developed a computer-controlled bioreactor system to study various aspects of microbially-mediated nitrogen cycling. The system has been used to investigate methods for controlling microbial denitrification (the dissimilatory reduction of nitrate to N2O and N2) in hydroponic plant growth chambers. Such chambers are key elements of advanced life support systems being designed for use on long duration space missions, but nitrogen use efficiency in them is reduced by denitrification. Control software architecture was designed which permits the heterogeneous control of system hardware using traditional feedback control, and quantitative and qualitative models of various system features. Model-based feed forward control entails prediction of future systems in states and automated regulation of system parameters to achieve desired and avoid undesirable system states. A bacterial growth rate model based on the classic Monod model of saturation kinetics was used to evaluate the response of several individual denitrifying species to varying environmental conditions. The system and models are now being applied to mixed microbial communities harvested from the root zone of a hydroponic growth chamber. The use of a modified Monod organism interaction model was evaluated as a means of achieving more accurate description of the dynamic behavior of the communities. A minimum variance parameter estimation routine was also' used to calibrate the constant parameters in the model by iterative evaluation of substrate (nitrate) uptake and growth kinetics. This representation of processes and interactions aids in the formulation of control laws. The feed forward control strategy being developed will increase system autonomy, reduce crew intervention and limit the accumulation of undesirable waste products (NOx).

Smernoff, David T.↗

NASA NTRS2007

Spaceflight Alters Bacterial Gene Expression and Virulence and Reveals Role for Global Regulator Hfq

A comprehensive analysis of both the molecular genetic and phenotypic responses of any organism to the spaceflight environment has never been accomplished due to significant technological and logistical hurdles. Moreover, the effects of spaceflight on microbial pathogenicity and associated infectious disease risks have not been studied. The bacterial pathogen Salmonella typhimurium was grown aboard Space Shuttle mission STS-115 and compared to identical ground control cultures. Global microarray and proteomic analyses revealed 167 transcripts and 73 proteins changed expression with the conserved RNA-binding protein Hfq identified as a likely global regulator involved in the response to this environment. Hfq involvement was confirmed with a ground based microgravity culture model. Spaceflight samples exhibited enhanced virulence in a murine infection model and extracellular matrix accumulation consistent with a biofilm. Strategies to target Hfq and related regulators could potentially decrease infectious disease risks during spaceflight missions and provide novel therapeutic options on Earth.

Wilson, J. W.↗

NASA NTRS2003

Multi-scale variation in spatial heterogeneity for microbial community structure in an eastern Virginia agricultural field

To better understand the distribution of soil microbial communities at multiple spatial scales, a survey was conducted to examine the spatial organization of community structure in a wheat field in eastern Virginia (USA). Nearly 200 soil samples were collected at a variety of separation distances ranging from 2.5 cm to 11 m. Whole-community DNA was extracted from each sample, and community structure was compared using amplified fragment length polymorphism (AFLP) DNA fingerprinting. Relative similarity was calculated between each pair of samples and compared using geostatistical variogram analysis to study autocorrelation as a function of separation distance. Spatial autocorrelation was found at scales ranging from 30 cm to more than 6 m, depending on the sampling extent considered. In some locations, up to four different correlation length scales were detected. The presence of nested scales of variability suggests that the environmental factors regulating the development of the communities in this soil may operate at different scales. Kriging was used to generate maps of the spatial organization of communities across the plot, and the results demonstrated that bacterial distributions can be highly structured, even within a habitat that appears relatively homogeneous at the plot and field scale. Different subsets of the microbial community were distributed differently across the plot, and this is thought to be due to the variable response of individual populations to spatial heterogeneity associated with soil properties. c2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

NASA Discipline Life Support Systems↗

NASA NTRSDate not supplied

Lessons from Earth Bioaerosol Sampling for Venus Habitability & Biosignature Science

Venus’s clouds are often discussed as a potential habitat. Several high-priority science goals – cloud aerosol composition, internal radiative flux, and aerosol residence time and circulation models – will improve our understanding of Venus in an astrobiology context. Lessons from Earth’s aerobiosphere can inform these requirements and interpretation of results. A stable Venus aerobiosphere would need microorganisms to reproduce faster than they settle out due to gravity. This is a joint constraint of the potential nutrients and energy influx, bioenergetic costs such as desiccation and radiation damage, and aerosol dynamics. Though life cycles involving S- and Fe-based redox metabolism have been proposed, at an optimistic estimate of 75% H2SO4, Venus aerosol water activity (aw) is still ~0.02, far below the observed microbial growth limit of ~0.6. Long-term desiccation with brief spurts of repair, growth and reproduction in response to transient water influx (perhaps volcanism) is the most likely model for Earth-like life on Venus – a ‘desert bloom’ scenario. In Earth’s troposphere, clouds can carry 103 – 105 cells/mL, some metabolically active. A better analogue may be Earth’s stratospheric sulfate aerosol layer: supercooled sulfuric acid aerosols (acid weight fraction 0.6 – 0.85, 0.1 – 1 µm diameter, 0.1 – 1 cm-3) with little water activity, long residence times, high UV radiation, and only sporadic influx from surface particle sources. Viable cells isolated from this region are rare (~102 cells/m3), though ‘hot spots’ at tropospheric mixing occur. Cells are primarily in inactive forms such as spores, and it is unclear if any are associated with sulfate aerosols or simply co-located. Given the heterogeneities in Venus clouds and the model of a sparse, largely dormant ecosystem, a single transect on descent would most likely pass through a low-water, inactive region, missing potential signs of habitability or biosignatures. Even a passive aerial platform (balloon) may end up following a single air mass over its lifetime. A better strategy for Venus would target an aerial region with some upwelling from surface sources, and take multiple transects separated in time and space. Earth’s stratospheric bioaerosol population could provide a starting point for estimating the required lower volume and detection limits.

Earth↗

NASA NTRSDate not supplied

Agent-based modeling of microbes in space

Space is tough on organisms. Microorganisms traveling to space experience stress from environmental features such as ionizing radiation and lack of normal microgravity; however, much remains unknown about the mechanisms by which those environmental features affect microbial physiology. Microbes experience changes in gravity not directly but rather through changes in their fluid environment, and deep-space particle radiation causes cell damage that is complex but rare. Computational modeling at the single-cell level (agent-based modeling) can allow us to probe the spatially heterogeneous processes that characterize space stresses, to gain insight into the relationships of microbial cells with their environments and with each other. Here we present two software packages for simulating microbial population dynamics in space conditions: CAMDLES and AMMPER. Microbes growing in liquid culture medium in the microgravity of an orbital space station experience a quiescent, poorly-mixed fluid environment. CAMDLES (CFD-DEM Artificial Microgravity Developments for Living Ecosystem Simulation) simultaneously simulates biological, chemical, and mechanical processes to predict microbial ecological dynamics in microgravity, and in the rotating culture vessels used to create an artificial microgravity environment in the lab. Initial results demonstrate that the growth of a cross-feeding microbial consortium, dependent on the exchange of soluble metabolites, is sensitive to the initial spatial distribution of cells, and grows differently in real versus artificial microgravity. Microbial populations exposed to deep-space radiation experience spatially and temporally heterogeneous damage from the traversal of high-energy particles. AMMPER (Agent-Based Model for Microbial Populations Exposed to Radiation) pairs a 3d model of energy deposition along a radiation particle track with a microbial population growth and damage model to predict the effects of localized radiation damage on population-level responses. It includes a user-friendly graphical interface. AMMPER results agree with experimental data indicating that indirect effects of radiation (reactive oxygen species generation, metabolic impairment) have a greater impact on microorganisms than direct effects (DNA damage).

Jessica A Lee↗

NASA NTRS2022

Agent-Based Modeling of Microbes in Space

Space is tough on organisms. Microorganisms traveling to space experience stress from environmental features such as ionizing radiation and lack of normal gravity, and much remains unknown about the mechanisms by which those environmental features affect microbial physiology. Microbes experience changes in gravity not directly but rather through changes in their fluid environment, and deep-space particle radiation causes cell damage that is complex but rare. Computational modeling at the single-cell level (agent-based modeling) can allow us to probe the spatially heterogeneous processes that characterize space stresses, to gain insight into the relationships of microbial cells with their environments and with each other. Here we present two software packages for simulating microbial population dynamics in space conditions: CAMDLES and AMMPER. Microbes growing in liquid culture medium in the microgravity of an orbital space station experience a quiescent, poorly-mixed fluid environment. CAMDLES (CFD-DEM Artificial Microgravity Developments for Living Ecosystem Simulation) simultaneously simulates biological, chemical, and mechanical processes to predict microbial ecological dynamics in microgravity, and in the rotating culture vessels used to create an artificial microgravity environment in the lab. Initial results demonstrate that the growth of a cross-feeding microbial consortium, dependent on the exchange of soluble metabolites, is sensitive to the initial spatial distribution of cells, and grows differently in real versus artificial microgravity. Microbial populations exposed to deep-space radiation experience spatially and temporally heterogeneous damage from the traversal of high-energy particles. AMMPER (Agent-Based Model for Microbial Populations Exposed to Radiation) pairs a 3d model of energy deposition along a radiation particle track with a microbial population growth and damage model to predict the effects of localized radiation damage on population-level responses. It includes a user-friendly graphical interface. AMMPER growth curves recapitulate experimental results, and allow comparison between direct effects (DNA damage) and indirect effects (reactive oxygen species generation, metabolic impairment) of radiation.

microbiology↗

NASA NTRS1988

The cryptoendolithic microbial environment in the Ross Desert of Antarctica: light in the photosynthetically active region

The vertical zonation of the Antarctic cryptoendolithic community appears to form in response to the light regime in the habitat. However, because of the structure of the habitat, the light regime is difficult to study directly. Therefore, a mathematical model of the light regime was constructed, which was used to estimate the total photon flux in different zones of the community. Maximum fluxes range from about 150 micrometers photons m-2 s-1 at the upper boundary of the community to about 0.1 micrometer photons m-2 s-1. Estimates of the annual productivity in the community indicate that the lowest zone of the community is light limited, with the maximal annual carbon uptake equivalent to less than the carbon content of one algal (Hemichloris) cell.

NASA Discipline Number 52-30↗

NASA NTRS2014

Efficacy of Antimicrobials on Bacteria Cultured in a Spaceflight Analogue

As humans travel in space, they will interact with microbial flora from themselves, other crewmembers, their food, and the environment. While evaluations of microbial ecology aboard the Mir and ISS suggest a predominance of common environmental flora, the presence of (and potential for) infectious agents has been well documented. Likewise, pathogens have been detected during preflight monitoring of spaceflight food, resulting in the disqualification of that production lot from flight. These environmental and food organisms range from the obligate pathogen, Salmonella enterica serovar Typhimurium (S. Typhimurium), which has been responsible for disqualification and removal of food destined for ISS and has previously been reported from Shuttle crew refuse, to the opportunistic pathogen Staphylococcus aureus, isolated numerous times from ISS habitable compartments and the crew. Infectious disease events have affected spaceflight missions, including an upper respiratory infection that delayed the launch of STS-36 and an incapacitating Pseudomonas aeruginosa urinary tract infection of a crewmember during Apollo 13. These observations indicate that the crew has the potential to be exposed to obligate and opportunistic pathogens. This risk of exposure is expected to increase with longer mission durations and increased use of regenerative life support systems. As antibiotics are the primary countermeasure after infection, determining if their efficacy during spaceflight missions is comparable to terrestrial application is of critical importance. The NASA Rotating Wall Vessel (RWV) culture system has been successfully used as a spaceflight culture analogue to identify potential alterations in several key microbial characteristics, such as virulence and gene regulation, in response to spaceflight culture. We hypothesized that bacteria cultured in the low fluid shear RWV environment would demonstrate changes in efficacy of antibiotics compared to higher fluid shear controls. This study investigated the response of three medically significant microorganisms grown in the RWV to antibiotics that could be used on spaceflight missions. Our findings suggest potential alterations in antibiotic efficacy during spaceflight and indicate that future studies on the antibiotic response require additional basic research using the RWV and/or true spaceflight. However, while this analogue has reinforced these potential alterations, the results suggest the best approach for applied forward work is evaluating an in vivo system during spaceflight, including human and rodent studies. The complex nature of the analysis for many antibiotics and organism suggests the best approach to determine in vivo responses during pharmaceutical treatment is evaluating an in vivo system during spaceflight.

Nickerson, CA↗

NASA NTRS1991

A serum factor promotes collagenase synthesis by an osteoblastic cell line

Regulation of the synthesis of collagenase was investigated in the osteoblastic cell line, UMR 106-01. The cells were stained by the avidin-biotin-complex technique for the presence of the enzyme. By this method, it was possible to identify cells producing collagenase. Synthesis, but not secretion, was found to be constitutive in these cells with the enzyme located intracellularly in cytoplasmic vesicles and the Golgi apparatus. The amount of collagenase contained within UMR cells and the number of cells synthesizing the enzyme were proportional to the concentration of fetal bovine serum in the incubating medium. When serum was withdrawn from the osteosarcoma cells, the content of collagenase decreased with time and the enzyme became undetectable by 48 h of serum depletion. The decrease in collagenase content could be completely reversed by resupplying serum to the cells. The collagenase promoting activity of serum could not be eliminated by adsorption on activated charcoal but was retained by a dialysis membrane with a 12,000 mol wt cutoff. A range of bone-seeking hormones or agents known to affect collagenase secretion was added to the medium in an attempt to mimic the effect of serum on collagenase accumulation. None of these agonists, including parathyroid hormone, could reproduce the effect of serum on these cells, although parathyroid hormone could act as a collagenase secretagogue in the presence or absence of serum. It is concluded that fetal bovine serum contains a yet unidentified factor or factors greater than 12,000 mol wt responsible for the continued synthesis of collagenase by UMR 106-01 cells.

Non-NASA Center↗

NASA NTRS1980

Endolithic microbial life in hot and cold deserts

Endolithic microorganisms (those living inside rocks) occur in hot and cold deserts and exist under extreme environmental conditions. These conditions are discussed on a comparative basis. Quantitative estimates of biomass are comparable in hot and cold deserts. Despite the obvious differences between the hot and cold desert environment, survival strategies show some common features. These endolithic organisms are able to 'switch' rapidly their metabolic activities on and off in response to changes in the environment. Conditions in hot deserts impose a more severe environmental stress on the organisms than in the cold Antarctic desert. This is reflected in the composition of the microbial flora which in hot desert rocks consist entirely of prokaryotic microorganisms, while under cold desert conditions eukaryotes predominate.

Friedmann, E. I.↗

NASA NTRS2012

Microbial Monitoring of Pathogens by Comparing Multiple Real-Time PCR Platforms for Potential Space Applications

The International Space Station (ISS) is a closed environment wi~h rotations of crew and equipment each introducing their own microbial flora making it necessary to monitor the air, surfaces, and water for microbial contamination. Current microbial monitoring includes labor and time intensive methods to enumerate total bacterial and fungal cells with limited characterization during in-flight testing. Although this culture-based method has been sufficient for monitoring the ISS, future long duration missions will need to perform more comprehensive characterization in-flight, since sample return and ground characterization may not be available. A workshop was held in 2011 at the Johnson Space Center to discuss alternative methodologies and technologies suitable for microbial monitoring for these longterm exploration missions where molecular-based methodologies, such as polymerase chain reaction (PCR), were recommended. In response, a multi-center (Marshall Space Flight Center, Johnson Space Center, Jet Propulsion Laboratory, and Kennedy Space Center) collaborative research effort was initiated to explore novel commercial-off-the-shelf hardware options for spaceflight environmental monitoring. The goal was to evaluate quantitative/semi-quantitative PCR approaches to space applications for low cost in-flight rapid identification of microorganisms affecting crew safety. The initial phase of this project identified commercially available platforms that could be minimally modified to perform nominally in microgravity followed by proof-of-concept testing on the highest qualifying candidates with a universally available test organism, Salmonella enterica. The platforms evaluated during proof-of-concept testing included the iCubate 2.0(TradeMark) (iCubate, Huntsville, AL), RAZOR EX (BioFire Diagnostics; Salt Lake City, Utah) and SmartCycler(TradeMark) (Cepheid; Sunnyvale, CA). The analysis identified two potential technologies (iCubate 2.0 and RAZOR EX) that were able to perform sample-to-answer testing with cell sample concentrations between SO to 400 cells. In addition, the commercial systems were evaluated for initial flight safety and readiness, sample concentration needs were reviewed, and a competitive procurement of commercially available platforms was initiated.

Birmele, Michele↗

NASA NTRS1998

Assessment of changes in microbial community structure during operation of an ammonia biofilter with molecular tools

Biofiltration has been used for two decades to remove odors and various volatile organic and inorganic compounds in contaminated off-gas streams. Although biofiltration is widely practiced, there have been few studies of the bacteria responsible for the removal of air contaminants in biofilters. In this study, molecular techniques were used to identify bacteria in a laboratory-scale ammonia biofilter. Both 16S rRNA and ammonia monooxygenase (amoA) genes were used to characterize the heterotrophic and ammonia-oxidizing bacteria collected from the biofilter during a 102-day experiment. The overall diversity of the heterotrophic microbial population appeared to decrease by 38% at the end of the experiment. The community structure of the heterotrophic population also shifted from predominantly members of two subdivisions of the Proteobacteria (the beta and gamma subdivisions) to members of one subdivision (the gamma subdivision). An overall decrease in the diversity of ammonia monooxygenase genes was not observed. However, a shift from groups dominated by organisms containing Nitrosomonas-like and Nitrosospira-like amoA genes to groups dominated by organisms containing only Nitrosospira-like amoA genes was observed. In addition, a new amoA gene was discovered. This new gene is the first freshwater amoA gene that is closely affiliated with Nitrosococcus oceanus and the particulate methane monooxygenase gene from the methane oxidizers belonging to the gamma subdivision of the Proteobacteria.

NASA Discipline Life Support Systems↗

NASA NTRS2000

Microgravity as a novel environmental signal affecting Salmonella enterica serovar Typhimurium virulence

The effects of spaceflight on the infectious disease process have only been studied at the level of the host immune response and indicate a blunting of the immune mechanism in humans and animals. Accordingly, it is necessary to assess potential changes in microbial virulence associated with spaceflight which may impact the probability of in-flight infectious disease. In this study, we investigated the effect of altered gravitational vectors on Salmonella virulence in mice. Salmonella enterica serovar Typhimurium grown under modeled microgravity (MMG) were more virulent and were recovered in higher numbers from the murine spleen and liver following oral infection compared to organisms grown under normal gravity. Furthermore, MMG-grown salmonellae were more resistant to acid stress and macrophage killing and exhibited significant differences in protein synthesis than did normal-gravity-grown cells. Our results indicate that the environment created by simulated microgravity represents a novel environmental regulatory factor of Salmonella virulence.

NASA Discipline Environmental Health↗