So how do you grow plants in space? Well, Veggie is a great growth chamber that can control the humidity, temperature, and carbon dioxide for plants. So the researchers asked astronauts to grow red romaine lettuce using Veggie. They had 3 crops grown over 3 consecutive years. At the same time, crops were growing on the ISS, the researchers grew the same type of crops on Earth under the same conditions as in Veggie.

The researchers and the astronauts both took samples from the leaves and roots of their crops and then tested everything for E. coli and Salmonella. They also used their samples to grow bacteria from the lettuce in the lab on petri dishes. Then they isolated DNA from the colonies and compared them to a database to figure out what types of bacteria were there. But some bacteria won’t grow on petri dishes so they also used their original samples to directly isolate DNA.

The last thing they did was to test the nutrient content of the lettuce.