Biological Research in Canisters Symbiotic Nodulation in a Reduced Gravity Environment (BRIC-SyNRGE) - 07.14.16
Biological Research in Canisters Symbiotic Nodulation in a Reduced Gravity Environment (BRIC-SyNRGE) investigates microgravity effects associated with microbe-host interactions and cell-cell communication using a plant-bacteria model system. Medicago truncatula (barrel medic) seedlings are grown on-orbit in the presence of genetically marked strains of nitrogen-fixing bacteria of the species Sinorhizobium meliloti. These bacteria are able to form a mutualistic symbiosis (relationship between different species in which both benefit) with leguminous plants. On Earth, this symbiotic plant-bacteria relationship benefits both crops for humans and livestock. Science Results for Everyone
Information Pending Experiment Details
Gary W. Stutte, Ph.D., Limerick Institute of Technology, Limerick, Ireland
Michael S. Roberts, Ph.D., Dynamac Corporation, Kennedy Space Center, FL, United States
QinetiQ North America (Engineering Services Contract), Cape Canaveral, FL, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
March 2011 - September 2011
STS-87, STS-107, and STS-131.
- Such foods as soybean, peas, beans, alfalfa and clover rely on bacterial symbiosis when grown in nitrogen depleted soil. A better understanding of this relationship will increase our knowledge base of both microgravity plant growth as well as agricultural applications on Earth.
- Biological Research in Canisters Symbiotic Nodulation in a Reduced Gravity Environment (BRIC-SyNRGE) tests the hypothesis that the rate of infection of Medicago truncatula by Sinorhizobium meliloti is higher in microgravity than in 1g. In addition, mechanistic responses that trigger host-symbiont signaling and infection are identified. Lastly, physiological responses due to changes in the plant systemic response (host immunity) or infection by bacteria (virulence) are examined.
- This plant-bacteria symbiotic relationship is established by the bacteria infecting plant root hairs and then by the plant forming specialized nodules where the bacteria can convert atmospheric nitrogen into a form the plants can use to produce proteins. This symbiosis in legumes accounts for approximately 20 percent of global biological nitrogen fixed annually. The legumes are a major direct source of food for man (soybean, peas, beans, etc.) and forage for livestock (alfalfa, Medicago, clover, vetch, etc.), and therefore, represent a critical contribution to world food production.
Biological Research in Canisters Symbiotic Nodulation in a Reduced Gravity Environment (BRIC-SyNRGE) investigates microgravity effects associated with microbe-host interactions and cell-cell communication using a plant-bacteria model system. Seeds from a single cultivar (plant selected for desirable characteristics) of the model legume species Medicago truncatula (barrel medic) is germinated on-orbit in the presence of genetically marked strains of nitrogen-fixing bacteria of the species Sinorhizobium meliloti capable of forming a mutualistic endosymbiosis (beneficial relationship in which one organism lives within the body or cells of another organism) with leguminous plants. Cellular, molecular, and morphological analyses of plant tissue specimens and bacteria fixed on-orbit are compared to ground controls to elucidate the effect of microgravity on plant and bacterial physiological responses, mechanisms of cell-cell communication and resource exchange (i.e., carbon and nitrogen), and the extent of symbiotic nodule formation. Symbiotic nitrogen-fixing bacteria and leguminous plants have evolved complex signal exchange mechanisms that enable specific bacterial species to induce specific host plant species to form invasion structures through which the bacterium enters the plant root. Once inside, the bacteria are enclosed within a micro-aerobic cell compartment by the host plant and differentiate into specialized cells that express an oxygen-sensitive enzyme to catalyze the conversion of nitrogen to ammonia for use by the host plant. Although the rhizobia-legume microbe-host relationship is mutually beneficial, rhizobial infections of plants can be deleterious. Rhizobia are similar to Brucella spp. that infect animals (including humans) in that they both form chronic infections of eukaryotic cells within a host-derived membrane compartment and require host-derived factors for survival within the host. Based on recent reports of increased virulence of Salmonella typhimurium, Pseudomonas aeruginosa, and Streptococcus pneumoniae in reduced gravity, differences in the infectious and/or pathogenic responses of rhizobial bacteria or the systemic acquired resistance of the host plant are also likely.
BRIC-SynRGE aims to:
- Determine if S. meliloti successfully infects and nodulates M. truncatula to establish effective endosymbiosis in space flight.
- Determine whether there is an increase in virulence in S. meliloti and/or reduced systemic plant resistance in M. truncatula under microgravity conditions.
- Identify changes in gene expression in host that are associated with infection and/or nodulation in microgravity.
- Determine whether symbiosis occurs, and carbon/nitrogen exchange occurs between organisms.
The BRIC-SyNRGE hardware flying on STS-135 utilizes reflown and series BRIC hardware to provide the following:
- A sterile environment for Medicago truncatula seedling growth.
- A delivery system capable of fixative delivery prior to reentry.
- Three redundant levels of containment for hazardous materials.
- Autonomous temperature data logging.
BRIC-SyNRGE directly addresses the impact of the space environment on microbial virulence in a constructed ecosystem. The establishment of a controlled environment, legume-rhizobium ecosystem, to utilize biological fixation to recycle nitrogen and reduce food resupply benefits long-duration transit and planetary surface habitation missions. Preliminary work has indicated that establishment of the legume-rhizobium ecosystem enables Martian regolith (loose material covering rock) stimulants to support plant growth. The M. truncatula-S. meliloti system is a well-defined biological model system for studying plant/microbe interactions and the biological and genomic tools are available to determine whether the virulence of S. meliloti is increased in the space environment. BRIC-SyNRGE is designed to directly test the hypothesis that the virulence of S. meliloti is increased in microgravity. BRIC-SyNRGE is designed to use molecular, biochemical and microscopic tools to determine whether a change in virulence is due to reduced resistance of the host, increased virulence of the microorganism, or changes in the signal transduction pathway.
Plant-bacteria symbiosis accounts for a large percentage of human and livestock food production on Earth, particularly in nitrogen-depleted soil. BRIC-SyNRGE adds to the knowledge base of this plant-bacteria mechanism.
Operational Requirements and Protocols
BRIC-SyNRGE operates largely autonomously. No on-orbit power, active cooling, or telemetry are required. One, ten-minute crew operation is performed before docking to transfer the BRICs from Coldbags to their ambient locker location. Later, at return minus two days (R-2), the crew performs a 40-minute Actuation procedure, including restowing the BRICs, four in a Double Coldbag, and four at ambient in a middeck locker. All BRIC hardware remains on the Shuttle for the duration of the mission, and is be returned on STS-135.
BRIC-SyNRGE operates largely autonomously throughout all phases of flight, with minimal crew involvement during the on-orbit phase. BRIC requires no power, no active cooling and no telemetry. Prior to launch, the BRICs are cold-soaked to 4°C. Four BRICs are placed in each of two Double Coldbags. While cold, the seedlings inside the BRICs remain dormant. No icebricks are stowed in the Double Coldbags since they are intended to slowly warm to ambient to initiate seedling growth. Each Double Coldbag is stowed in a middeck locker. Stowed in a third locker is a BRIC half locker foam tray, with an Actuator Tool and Rod Kit.
Throughout ascent and the early days of the mission, the BRICs warm passively to ambient temperature and approximately six hours into flight and seedling growth begins. Though BRIC operates largely passively on-orbit, there are two scheduled crew operations. The BRICs remain stowed passively until Docked Operations when the Double Coldbags must be transferred to ISS inventory. At this time, the BRICs are unstowed, and moved to a third Middeck locker and placed in foam. They then remain passively stowed until post-docked operations.
At R-2, the crew perform an Actuation operation on four of the BRICs. Actuation is a mechanical procedure, which forces movement of fluids inside the PDFU. The crew is instructed to remove the Actuator Tool and Rod Kit from a separate middeck locker. A rod is removed from the Rod Kit and inserted in the Actuator Tool. The Actuator Tool is then threaded to the appropriate PDFU port on one of the BRIC–PDFU canisters. The handle is squeezed until the Actuator has sufficiently inserted the rod inside the PDFU. This process is repeated using a new rod for each of five PDFUs in four of the BRIC canisters. The fluid inside all 20 of these PDFUs is RNAlater, a chemical fixative. The triple-containment design precludes crew contact with fluids. All fluids and biological samples are contained within three levels of containment throughout all phases of flight.
When Actuation is completed, the four actuated BRICs are restowed in the Middeck locker foam cut-out at ambient. The four BRICs, which were not actuated are stowed in a new, cold Double Coldbag, with icebricks. These four BRICs then cool to 4°C, returning the seedlings to a dormant state. These four BRICs do not contain chemical fixatives. Instead, the fluid volume is used for additional bacterial samples that are "brought back alive" for post-flight infection experiments.
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Medicago truncatula (barrel medic) leaf sample; brown markings show beneficial nodulation due to bacterial inoculation. Image courtesy of NASA.
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Biological Research In Canisters (BRIC) Canister, with five Petri Dish Fixation Units (PDFUs) and HOBO™ temperature data logger inside. Image courtesy of NASA.
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Biological Research In Canisters (BRIC) Actuator Tool attached to BRIC Canister during Actuation Operation. Image courtesy of NASA.
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Medicago truncatula (barrel medic) seedlings grown inside a Biological Research In Canisters (BRIC) Petri Dish Fixation Unit (PDFU). Image courtesy of NASA.
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