Scientists test bacteria's power to boost broccoli growth in space

A team of student researchers in the US has sent broccoli seeds to the International Space Station (ISS) to test whether microbes can help the vegetable grow better in the challenging conditions in space.

The goal of the experiment, conducted by students at Valley Christian High School in San Jose, California, is to learn how to grow vegetables in the microgravity conditions of the space station -- and eventually on the Moon and Mars -- as human space exploration expands.

The six broccoli seeds were sent aboard the Orbital ATK Cygnus spacecraft which delivered more than three tonnes of supplies to the crew aboard the ISS on May 24.

Three of the seeds were sent to space as is, while the other three were coated with two different species of bacteria developed at the University of Washington that can live inside crop plants and improve their growth.

These "beneficial" microbes, also called endophytes, may also help plants grow better in extreme low-gravity environments, and where nutrients or water could be lacking, according to a statement released by the university.

"It would be ideal if we could grow crops for astronauts at the space station or who are lunar- or Mars-based without needing to ship potting mix or fertilizer," said Sharon Doty, Professor at the University of Washington, Seattle.

"We would like to be able to get plants to grow in what is available with a minimum input," Doty added.

The students are participating in Quest Institute for Quality Education's "Quest for Space" programme and are mentored by David Bubenheim of NASA-Ames Research Center's Biospheric Science Branch and John Freeman of Intrinsyx Technologies.

The experiment was prepped in a flight laboratory located at NASA-Ames Research Center in California.

"In space, plants are very stressed and don't grow or reproduce well," Freeman explained.

"We want plants to grow better. We are trying broccoli because it's considered an anti-carcinogenic food source that is a good dietary candidate for deep-space explorers," Freeman said.

While a number of different vegetable growing experiments have been conducted aboard the ISS, this is the first that studies natural microbes to possibly help plants grow under nutrient limitations and in microgravity.

The microbes are first encapsulated inside a coating that covers the broccoli seeds, which protects the seeds from dehydration and allows for safe dry storage before the seeds are hydrated and grown in orbit.

At the space station, the seeds will be hydrated in a small plant-growth chamber that provides constant light to promote photosynthesis.

After the plants return from space, the students will measure their growth and chlorophyll content and compare the inoculated broccoli to those that were grown without microbes.

Separately, Doty and her team will receive plant samples to investigate how well the two microbe species colonised the broccoli in space, and whether they were as effective as when grown on Earth.

"We want to know whether the microbes still find their way inside the plant even in microgravity, and if any of the required plant signals are terrestrial-based," Doty said.

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