Salads may create life-threatening issues in space

Salad is generally considered a healthy food, even for space travelers. It seems like growing fresh greens in orbit could be a great way for astronauts to maintain their health. However, recent research suggests that growing leafy plants like lettuce and spinach in space might pose a risk to astronauts. According to a study conducted by researchers at the University of Delaware, these plants are more susceptible to the Salmonella enterica pathogen when grown in simulated microgravity conditions. This means that growing space salad could come with a side dish of bacteria.

We already know that the International Space Station (ISS) is home to many aggressive bacteria and fungi. If these space microbes were to cause widespread sickness among the astronaut crew, it would put their lives at risk.

“You don’t want the whole mission to fail just because of a food safety outbreak,” says plant biologist Harsh Bais from the University of Delaware.

Bais and his team conducted an experiment using a clinostat device to simulate the microgravity conditions in a lab. They put lettuce plants in these state and added S. enterica bacteria to the leaves. Surprisingly, the stomata pores in the lettuce opened up, allowing the bacteria to invade, even though the stomata’s job is to prevent attackers from entering the plant while helping it breathe.
The researchers then added a more helpful species of bacteria that usually defends plants from external stressors. However, the defenses did not work in microgravity, indicating that there’s something about this state that disables the lettuce’s chemical reactions that keep it safe.

“The fact that [the stomata] were remaining open when we were presenting them with what would appear to be a stress was really unexpected,” says plant scientist Noah Totsline from the University of Delaware.

‘In effect, the plant would not know which way was up or down. We were somewhat confusing their response to gravity.’
Previous studies have shown that space-grown lettuce is just as safe and nutritious as the ones grown on Earth. However, recent research indicates that space lettuce may struggle to protect itself from infections in the usual way.
Given that space bacteria are known to be particularly harmful, this could pose a potential problem. The research team is calling for more research into ensuring the safety of our food in space, with genetic modifications being one possible solution.”

“We need to be prepared for and reduce risks in space for those living now on the International Space Station and for those who might live there in the future,” says University of Delaware microbiologist Kali Kniel.

It is important to understand how bacterial pathogens react to microgravity in order to develop appropriate mitigation strategies.

This news is a creative derivative product from articles published in famous peer-reviewed journals and Govt reports:

1. Totsline, N., Kniel, K.E., Sabagyanam, C. et al. Simulated microgravity facilitates stomatal ingression by Salmonella in lettuce and suppresses a biocontrol agent. Sci Rep 14, 898 (2024).
2. Carillo, P., Morrone, B., Fusco, G. M., De Pascale, S. & Rouphael, Y. Challenges for a sustainable food production system on board of the International Space Station: A technical review. Agronomy 10, 687 (2020).
3. Sharma, S. et al. Vegetable microgreens: The gleam of next generation super foods, their genetic enhancement, health benefits and processing approaches. Food Res. Int. 155, 111038 (2022).
4. Urbaniak, C. et al. Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces. Sci. Rep. 8, 814 (2018).
5. Checinska Sielaff, A. et al. Characterization of the total and viable bacterial and fungal communities associated with the International Space Station surfaces. Microbiome 7, 50 (2019).

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