Lettuce crops grown in the Veggie payload aboard ISS harvested and returned for chemical microbiological and molecular analysis

Lettuce crops grown in the Veggie payload aboard ISS harvested and returned for chemical microbiological and molecular analysis

Lettuce crops grown in the Veggie payload aboard ISS, harvested and returned for chemical, microbiological and molecular analysis

The ability to grow safe, fresh food to supplement packaged foods of astronauts in space has been an important goal for NASA. Food crops grown in space experience different environmental conditions than plants grown on Earth (e.g., reduced gravity, elevated radiation levels). To study the effects of space conditions, red romaine lettuce, Lactuca sativa cv ‘Outredgeous,’ plants were grown in Veggie plant growth chambers on the International Space Station (ISS) and compared with ground-grown plants. Multiple plantings were grown on ISS and harvested using either a single, final harvest, or sequential harvests in which several mature leaves were removed from the plants at weekly intervals. Ground controls were grown simultaneously with a 24–72 h delay using ISS environmental data. Food safety of the plants was determined by heterotrophic plate counts for bacteria and fungi, as well as isolate identification using samples taken from the leaves and roots. Molecular characterization was conducted using Next Generation Sequencing (NGS) to provide taxonomic composition and phylogenetic structure of the community. Leaves were also analyzed for elemental composition, as well as levels of phenolics, anthocyanins, and Oxygen Radical Absorbance Capacity (ORAC). Comparison of flight and ground tissues showed some differences in total counts for bacteria and yeast/molds (2.14 – 4.86 log10 CFU/g), while screening for select human pathogens yielded negative results. Bacterial and fungal isolate identification and community characterization indicated variation in the diversity of genera between leaf and root tissue with diversity being higher in root tissue, and included differences in the dominant genera. The only difference between ground and flight experiments was seen in the third experiment, VEG-03A, with significant differences in the genera from leaf tissue. Flight and ground tissue showed differences in Fe, K, Na, P, S, and Zn content and total phenolic levels, but no differences in anthocyanin and ORAC levels. This study indicated that leafy vegetable crops can produce safe, edible, fresh food to supplement to the astronauts’ diet, and provide baseline data for continual operation of the Veggie plant growth units on ISS.

The ability to grow safe, fresh food to supplement packaged foods of astronauts in space has been an important goal for NASA. Food crops grown in space experience different environmental conditions than plants grown on Earth (e.g., reduced gravity, elevated radiation levels). To study the effects of space conditions, red romaine lettuce, Lactuca sativa cv ‘Outredgeous,’ plants were grown in Veggie plant growth chambers on the International Space Station (ISS) and compared with ground-grown plants. Multiple plantings were grown on ISS and harvested using either a single, final harvest, or sequential harvests in which several mature leaves were removed from the plants at weekly intervals. Ground controls were grown simultaneously with a 24–72 h delay using ISS environmental data. Food safety of the plants was determined by heterotrophic plate counts for bacteria and fungi, as well as isolate identification using samples taken from the leaves and roots. Molecular characterization was conducted using Next Generation Sequencing (NGS) to provide taxonomic composition and phylogenetic structure of the community. Leaves were also analyzed for elemental composition, as well as levels of phenolics, anthocyanins, and Oxygen Radical Absorbance Capacity (ORAC). Comparison of flight and ground tissues showed some differences in total counts for bacteria and yeast/molds (2.14 – 4.86 log10 CFU/g), while screening for select human pathogens yielded negative results. Bacterial and fungal isolate identification and community characterization indicated variation in the diversity of genera between leaf and root tissue with diversity being higher in root tissue, and included differences in the dominant genera. The only difference between ground and flight experiments was seen in the third experiment, VEG-03A, with significant differences in the genera from leaf tissue. Flight and ground tissue showed differences in Fe, K, Na, P, S, and Zn content and total phenolic levels, but no differences in anthocyanin and ORAC levels. This study indicated that leafy vegetable crops can produce safe, edible, fresh food to supplement to the astronauts’ diet, and provide baseline data for continual operation of the Veggie plant growth units on ISS.

Investigates the microbial communities of plants and Veggie pillow components with culturable and non-culturable methods providing qualitative and quantitative data. This studies also stresses the food safety component of fresh crops grown on the ISS. The VEG-03F technology demonstration took place within a Veggie unit on the International Space Station (ISS). Microbiological characterization using molecular methods was performed on leaves and roots from one harvest of red romaine lettuce (Lactuca sativa cv. ‘Outredgeous’) and associated rooting pillow components and Veggie chamber surfaces. Culture based enumeration and pathogen screening indicated the leafy greens were safe for consumption. Surface samples of the Veggie facility and plant pillows revealed low counts of bacteria and fungi and are commonly isolated on ISS. Community analysis was completed with 16S rRNA amplicon sequencing. Comparisons between pillow components, and plant tissue types from VEG-03D, E, and F revealed higher diversity in roots and rooting substrate than the leaves and wick. This work provides valuable information for food production-related research on the ISS and the impact of the plant microbiome on this unique closed environment.

Investigates the microbial communities of plants and Veggie pillow components with culturable and non-culturable methods providing qualitative and quantitative data. This studies also stresses the food safety component of fresh crops grown on the ISS. The VEG-03E technology demonstration was completed within a Veggie unit on the International Space Station (ISS). Microbiological characterization using molecular and culture-based methods was performed on leaves and roots from two harvests of green leaf lettuce, (Lactuca sativa cv. Waldmann’s) and associated rooting pillow components and Veggie chamber surfaces. Culture based enumeration and pathogen screening indicated the leafy greens were safe for consumption. Surface samples of the Veggie facility and plant pillows revealed low counts of bacteria and fungi and are commonly isolated on ISS. Community analysis was completed with 16S rRNA amplicon sequencing. Comparisons between pillow components, and plant tissue types from VEG-03D, E, and F revealed higher diversity in roots and rooting substrate than the leaves and wick. This work provides valuable information for food production-related research on the ISS and the impact of the plant microbiome on this unique closed environment.

Investigates the microbial communities of plants and Veggie pillow components with culturable and non-culturable methods providing qualitative and quantitative data. This studies also stresses the food safety component of fresh crops grown on the ISS. The VEG-03D technology demonstration was completed achieving simultaneous multi-species plant growth within a Veggie unit on the International Space Station (ISS). Microbiological characterization using molecular and culture-based methods was performed on leaves and roots from two harvests of three leafy greens, red romaine lettuce (Lactuca sativa cv. ‘Outredgeous’); mizuna mustard, (Brassica rapa var japonica); and green leaf lettuce, (Lactuca sativa cv. Waldmann’s) and associated rooting pillow components and Veggie chamber surfaces. Culture based enumeration and pathogen screening indicated the leafy greens were safe for consumption. Surface samples of the Veggie facility and plant pillows revealed low counts of bacteria and fungi and are commonly isolated on ISS. Community analysis was completed with 16S rRNA amplicon sequencing. Comparisons between pillow components, and plant tissue types from VEG-03D, E, and F revealed higher diversity in roots and rooting substrate than the leaves and wick. This work provides valuable information for food production-related research on the ISS and the impact of the plant microbiome on this unique closed environment.

The Space Algae Experiment Verification Test completed a competitive growth selection on mutagenized microalgae in a series of batch cultures that were passaged for three growth cycles. The experiment was conducted with ground control conditions similar to those actually used in spaceflight. Cultures were limited in growth rate due to gas permeable membranes to provide oxygen and carbon dioxide exchange and a lack of agitation to mix the cells throughout the liquid media. Two strains were grown and three biological replicates were completed for each strain. Specific variables (factors) tested were: 1) The effect of UVC mutagenesis was tested by sampling the algae cultures prior to mutagenesis. 2) The sensitivity of different strains was tested by conducting the experiment with a wild-type and cell wall mutant (cw15) strain. 3) The effect of competitive growth was tested by sampling each biological replicate experiment at the end of each growth cycle. 4) The effect of live culture storage in the dark was tested by sampling each growth cycle twice. At the time of passage a sample of cells was pelleted and frozen. The cultures were then stored in the dark in a Cargo Transport Bag (CTB) to simulate storage on the ISS and return of cultures. This factor tested whether cultures could be stored alive in the dark or if samples needed to be fixed at the time of passage in order to get an accurate representation of the genetic variation in each cycle of growth. Paired-end whole genome sequencing was completed for 38 samples: 2 strains pre mutagenesis and 2 strains X 3 biological replicates X 3 growth cycles X 2 storage conditions.

The whole-genome sequences of eight fungal strains that were selected for exposure to microgravity at the International Space Station are presented here. These baseline sequences will help to understand the observed production of novel bioactive compounds.