Researchers from the University of Delaware have shared new findings about lettuce grown aboard the International Space Station. The study, described in a peer-reviewed article in Scientific Reports, suggests that consuming space-grown lettuce alongside other vegetables could raise health concerns due to how microbes interact with plants in space conditions.
The central message is that microgravity appears to increase the vulnerability of crops grown on the ISS to microbes associated with the station environment. Among these microbes are strains linked to human health issues, including species related to E. coli and Salmonella.
To investigate these interactions, the team used a clinostat, a device that simulates weightlessness for plant samples, to study how lettuce responds to microbial exposure under conditions similar to spaceflight. The findings indicate that plants developed outside Earth’s gravity may be more prone to colonization by Salmonella.
Plants rely on tiny openings called stomata on stems and leaves to regulate gas exchange. Under Earth gravity, stomata can close as a defense when bacteria are detected.
In microgravity, however, lettuce plants showed a tendency for their stomata to remain open when microbes appeared. This failure to close stomata could help explain why space-grown lettuce might be more susceptible to bacterial intrusion than ground-grown crops.
Researchers also observed that even slow rotational motion within the facility could disrupt the plant’s defense signaling, effectively confusing the system meant to protect the foliage.
To reduce these risks, the study proposes practical steps such as disinfecting seeds before launch and evaluating crop genetics to minimize the tendency for stomatal openings under microgravity. These strategies aim to maintain plant health and microbial safety for crops destined for space environments.
In related lines of inquiry, scientists are exploring edible concepts for space farming, including simple salad combinations that could be produced from space-grown ingredients. This work supports the broader objective of sustaining long-term life-support systems beyond Earth.