Plants like lettuce could become very unhealthy if grown and eaten by astronauts in space, researchers find

Stuck up in the cramped quarters of the International Space Station, hundreds of kilometres from home, even the simplest Earthly joys become exotic treats. And grub, well, that's one of them.

Astronauts don't have a supermarket's worth of choices, but they do get things like flour tortillas and fancy instant coffee. And then there's space salad, a fancy bit of greens lovingly grown under controlled conditions. But their crunchy lettuce days may be numbered, as new research suggests it might not be the healthiest choice.

A group of researchers discovered that under simulated zero-gravity conditions, plants like lettuce, important for a balanced astronaut diet, become surprisingly hospitable to the likes of salmonella. You see, normally plants use their stomata like tiny trapdoors, breathing and keeping nasties like bacteria at bay. But when they tried to mimic space on Earth by spinning the lettuce plants like rotisserie chickens, something odd happened.

Instead of sensing danger and slamming the trapdoors shut, the plants' stomata flung open when exposed to the bacteria. This meant salmonella could waltz right into the leaf tissues under fake gravity fairly easily.

The team also tested a friendly bacteria called Bacillus subtilis UD1022, a plant protector down here on Earth. Unfortunately, in zero-gravity, even this valiant knight couldn't hold its own. Instead of helping the plants fight back, UD1022 seems to have gotten discombobulated by the space environment.

Despite the setbacks, the researchers have some promising ideas. Sterilising seeds and even giving the plants a genetic buff-up, like an immunity system upgrade, could be the key to creating super-resilient space lettuce that can withstand even the nastiest galactic nasties.