Evaluating microbial community profiles of Chile peppers grown on the International Space Station provides implications for fruiting crops

One of NASA's goals is growing edible crops in spaceflight to supplement the astronauts' diet with fresh, safe-to-eat vegetables. Growing plants in spaceflight presents challenges to achieve optimal plant growth and productivity. It is important to understand the optimal conditions for crops grown in spaceflight. The Advanced Plant Habitat (APH), an enclosed, environmentally controlled plant growth facility on the International Space Station (ISS) has been used to grow plants and monitors the environment. A technology demonstration mission on the ISS used the APH to grow chile peppers, Capsicum annuum, cv. NuMex Española Improved to maturity. Over 25 peppers were successfully harvested as a mix of red and green peppers at 109 and 137 days after initiation. Half of the fruit were consumed by the crew, and half were frozen at - 80 °C and returned with the science carrier (SC) to Kennedy Space Center, FL to determine microbial load and food safety. Bacterial and fungal counts, ranged from below detection limit to 111 CFU/gram fresh weight found on a single pepper only. Foodborne pathogens were not detected. Investigation of the communities using the V4 region of the 16S rRNA gene revealed taxonomic variations between the SC quadrants as well as between hardware components and plant tissues, indicating possible vertical or horizontal transfer of some bacteria. An investigation into the bacterial communities indicated 13 genera and 1 unidentified microbe as possible core microbiome components. In addition, bacteria such as Burkholderia and Sphingomonas previously identified from ISS water samples were present in the communities. This technology demonstration growing a long duration fruiting crop on the ISS provided verification of the pre-determined environmental conditions, contributed to the validation of the APHs' capability to support fruiting crops in space, and provided the crew a safe-to-eat addition to their pre-packaged diet. This technology demonstration may serve as a baseline for future space crop production systems or long duration spaceflight missions.