In a microgravity setting, such as the environment aboard the International Space Station (ISS), an ideal plant water delivery system is one that can grow edible crops with minimal resource consumption and minimal risk to crew members. There are also concerns associated with the ability to control fluid escape and biofilm formation resulting in potential dangers to systems, crops, or crewmembers. To identify an appropriate system, candidate systems were assembled and operated under simulated ISS environmental conditions (T,CO2,and RH) with red romaine lettuce (Lactuca sativa cultivar 'Outredgeous') as a model crop. Fluid reservoirs and randomly selected planting sites were sampled every seven days until maturity at which point edible plant biomass and root samples were also taken. Heterotrophic bacteria and fungi growth patterns throughout each planting cycle were determined by plate counts on appropriate agar media. The candidate systems were compared to a classic hydroponics system as a control and harvested crops were compared to controls as well as Veggie-grown and market produce. Plants harvested from candidate systems yielded lower average heterotrophic bacteria and fungi per gram of plant mass levels when compared to market and Veggie samples as well as those from the control system. Additional studies to evaluate the system sanitation regimen as well as testing additional crops should be considered to aid in the selection of an ideal system.
Abstract For long-term space missions, it is necessary to understand how organisms respond to changes in gravity. Plant roots are positively gravitropic; the primary root grows parallel to gravity's pull even after being turned away from the direction of gravity. We examined if this gravitropic response varies depending on the time of day reorientation occurs. When plants were reoriented in relation to the gravity vector or placed in simulated microgravity, the magnitude of the root gravitropic response varied depending on the time of day the initial change in gravity occurred. The response was greatest when plants were reoriented at dusk, just before a period of rapid growth, and were minimal just before dawn as the plants entered a period of reduced root growth. We found that this variation in the magnitude of the gravitropic response persisted in constant light (CL) suggesting the variation is circadian-regulated. Gravitropic responses were disrupted in plants with disrupted circadian clocks, including plants overexpressing Circadian-clock Associated 1 (CCA1) and elf3 -2, in the reorientation assay and on a 2D clinostat. These findings indicate that circadian-regulated pathways modulate the gravitropic responses, thus, highlighting the importance of considering and recording the time of day gravitropic experiments are performed.
Bioregenerative food systems that routinely produce fresh, safe-to-eat crops onboard spacecraft can supplement the nutrition and variety of shelf-stable spaceflight food systems for use during future exploration missions (i.e., low earth orbit, Mars transit, lunar, and Martian habitats). However, current space crop production systems are not yet sustainable because they primarily utilize consumable granular media and, to date, operate like single crop cycle, space biology experiments where root modules are sanitized prior to launch and discarded after each grow-out. Moreover, real-time detection of the cleanliness of crops produced in spacecraft is not possible. A significant paradigm shift is needed in the design of future space crop production systems, as they transition from operating as single grow-out space biology experiments to becoming sustainable over multiple cropping cycles. Soilless nutrient delivery systems have been used to demonstrate post-harvest sanitization and inflight microbial monitoring technologies to enable sequential cropping cycles in spacecraft. Post-harvest cleaning and sanitization prevent the buildup of biofilms and ensure a favorable environment for seedling establishment of the next crop. Inflight microbial monitoring of food and watering systems ensures food safety in spaceflight food systems. A sanitization protocol, heat sterilization at 60°C for 1 h, and soaking for 12 h in 1% hydrogen peroxide, developed in this study, was compared against a standard hydroponic sanitization protocol during five consecutive crop cycles. Each cropping cycle included protocols for the cultivation of a crop to maturity, followed by post-harvest cleaning and inflight microbial monitoring. Microbial sampling of nutrient solution reservoirs, root modules, and plants demonstrated that the sanitization protocol could be used to grow safe-to-eat produce during multiple crop cycles. The cleanliness of the reservoir and root module surfaces measured with aerobic plate counts was verified in near real time using a qPCR-based inflight microbial monitoring protocol. Post-harvest sanitization and inflight microbial monitoring are expected to significantly transform the design of sustainable bioregenerative food and life support systems for future exploration missions beyond low earth orbit (LEO).
Abstract In long-duration space missions, crops will supplement the astronaut diet. One proposed crop type is microgreens, the young seedlings of edible plants that are known for their high nutritional levels, intense flavors, colorful appearance, and variety of textures. While these characteristics make microgreens promising for space crop production, their small size presents a unique challenge within the microgravity environment. To address this challenge, a microgreen planting box was developed to improve microgreen harvest techniques both in 1 g and in microgravity without concern for contamination by roots. Using this microgreen planting box, three parabolic flights were conducted where two different bagging methods (attached and manual) and three different microgreen cutting methods (Guillotine, Pepper Grinder, Scissors) were tested. In flight, the microgreens were contained within a glovebox and footage of all microgreen harvests was recorded. Statistical and trade analyses revealed that the combination of Cutting & Bagging method that performed the best was the Pepper Grinder with attached bagging. This was based on the following criteria: (1) average execution time, (2) microgreen debris, (3) biomass yield, (4) root debris, (5) microgreens left on the hardware, (6) number of seedlings growing under the lids, (7) hardware failure, and (8) perceived ease of use. This process allowed us to identify weaknesses and strengths of all hardware types and helped us identify major points of improvement within the hardware design to harvest microgreens in microgravity. Future directions include microgreen harvests in analog environments and further development of microgreen Cutting & Bagging method.
ABSTRACT Adverse social experience affects social structure by modifying the behavior of individuals, but the relationship between an individual's behavioral state and its response to adversity is poorly understood. We leveraged naturally occurring division of labor in honey bees and studied the biological embedding of environmental threat using laboratory assays and automated behavioral tracking of whole colonies. Guard bees showed low intrinsic levels of sociability compared with foragers and nurse bees, but large increases in sociability following exposure to a threat. Threat experience also modified the expression of caregiving-related genes in a brain region called the mushroom bodies. These results demonstrate that the biological embedding of environmental experience depends on an individual's societal role and, in turn, affects its future sociability.
