We have been growing lettuce in space for years. Now we have discovered that they are more likely to make us sick

Bad news for astronauts who usually eat healthy. That is, for all astronauts. It has been almost ten years since the crew of the International Space Station consume vegetables they grow themselves in microgravity: lettuce, peppers, radishes. Some hot chili.

More recently, the astronauts of the chinese space stationwhich already has lettuce, cherry tomatoes and chiveseven though it hasn’t been in orbit that long. The problem is that space salads They are not as safe for consumption as we thought..

A team of researchers from the University of Delaware has discovered that lettuce and other vegetables grown in microgravity are more prone to contamination by bacteria such as Salmonella.

Until now, we thought that under microgravity conditions, plants tend to open their stomata (the small pores in their leaves and stems) more instead of closing them to prevent the invasion of pathogens.

However, a recent job from the same laboratory has discovered that at the entrance of Salmonella enterica in the tissue was independent of stomatal density, and that the factor that best predicts it is the variety (cultivar) of lettuce together with the microgravity itself.

Friendly bacteria also lose their protective effect

In previous studies, researchers explored the use of a friendly bacteria, B. subtilis, as a solution to the problem. However, the bacteria, which on Earth help plants fight pathogens, failed to protect them in it simulated microgravity environmentsuggesting that space significantly changes the interaction between plants and microbes.

The finding is important. Not only because it calls into question whether salads on the International Space Station are completely safe, but also because it helps understand the challenges of agriculture in future space colonies.

Now, anyway, we have another solution: use red lettuce. Probably, the higher content of phenols and antioxidants protects them from salmonella and the data suggests that selecting varieties with these traits could improve the food security of space crops.

With population growth on Earth and the loss of agricultural land, space is an increasingly realistic option for growing food. But if they want prevent a salmonellosis outbreakfuture space farmers better wash their hands thoroughly with soap and water.

A previous version of this article was published in February 2024

Image | NASA/Cory Huston

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