Plants need nitrogen, and that means fertilizers. However, fertilizers and fertilizer production are anything but environmentally friendly. That’s why researchers in Bayer’s joint venture Joyn Bio are exploring a new approach. They want to produce bacteria that could one day directly supply corn, wheat and rice plants with nitrogen.
Nitrogen fertilizers and their production are bad for the environment. But agriculture needs fertilizers to feed a growing global population.
Bayer’s Joyn Bio joint venture takes a completely new approach: the researchers are aiming to create bacteria that could one day directly supply corn, wheat and rice plants with nitrogen.
Bacteria that produce nitrogen compounds directly at the roots in a form that can be used by the plants could reduce fertilizer consumption by up to 40 percent.
Despite its relative abundance – elemental nitrogen makes up 78 percent of the air we breathe – most plants are unable to absorb and process nitrogen gas. To grow, they need soluble nitrogen compounds like ammonium and nitrates. Plants use these nitrogen compounds to manufacture the building blocks for their DNA, proteins and chlorophyll.
As a result, modern agriculture would be unthinkable without synthetic fertilizers made from ammonia (NH3). Nine out of ten farmers use artificial fertilizers. Ammonia is one of the top ten chemicals in the world by production volume. 85 percent of global NH3 production is used to manufacture fertilizers. The development of the Haber-Bosch process by Fritz Haber and Carl Bosch in the early years of the 20th century was a breakthrough for modern agriculture. Guillaume Barbier is director of the nitrogen fixation program at Joyn Bio, a biotech company co-founded by Ginkgo Bioworks and Bayer. As he explains, “This process was the first to produce ammonia from elemental nitrogen and hydrogen.”
Barbier and his colleagues are working to develop a more environmentally friendly, biological solution to replace industrial ammonia production. “The Haber-Bosch process and similar processes are very energy-intensive, which makes them harmful to the environment,” says Barbier. Chemical ammonia synthesis accounts for roughly two percent of global energy demand. Nitrogen fertilizers are responsible for 3 percent of global greenhouse gas emissions. “In the 20th century, we learned to use nitrogen fertilizers to feed the world’s growing population,” explains Joyn Bio CEO Mike Miille, “but even today, nitrogen fertilizer use is still not very efficient. Up to 50 percent leaches into the soil unused.” Joyn Bio has therefore set itself an ambitious goal, as Miille explains. “In the 21st century, we want to be able to feed the world sustainably, without harming the environment.”
Synthetic biology offers a route to a solution. By using the tools made available by this new discipline, the researchers hope to optimize microbes to perform specific tasks. “We’re looking, for example, for bacteria that can provide agricultural crops with a more sustainable nitrogen source than chemical nitrogen,” explains Miille. He and his colleagues are hoping that this approach will reduce fertilizer use by up to 40 percent. As Miille is keen to stress, “The science at present suggests that it is not yet possible to do away with fertilizers completely.”
Nature offers many examples of talented bacteria. Legumes, for example, a group that includes a wide range of species, live in a symbiotic relationship with bacteria in the Rhizobiaceae family. These bacteria colonize the root nodules of peas, beans, and pulses, where they produce nitrogen compounds in a form that can be absorbed by the plant. This allows the plants to thrive even on extremely nitrogenpoor soils. In return, the plants provide their little helpers with other nutrients. “We’re looking at a similar type of naturally occurring plant/microbes nutrient exchange,” explains Barbier. And the researchers have ambitious plans. The Joyn Bio team is using high-throughput techniques to analyze bacteria stored in Bayer’s library of 150,000 strains isolated from farm soils.
We want to understand which genes and metabolic pathways are involved in nitrogen fixation.
“We want to understand which genes and metabolic pathways are involved in nitrogen fixation. We then aim to optimize this naturally occurring biochemical process in bacteria specially designed for agricultural crops like cereals,” explains Barbier. But this presents a huge challenge for the team of bioengineers. Current research suggests that there are at least 20 genes involved in converting free nitrogen into ammonia. On top of this, there are also numerous minor nitrogen pathways. “The next step will be to increase the amount of nitrogen produced by our bacteria and to optimize them to meet the needs of individual crops,” explains Barbier.
Although optimized bacteria could in theory arise by chance through random genetic changes in the bacterial genome, this is unlikely. “Since the advent of industrial fertilizers, microbes that provide plants with nitrogen have no longer had any need to evolve in that direction,” explains Barbier. In fact, in these bacteria, most of the biochemical processes involved in nitrogen fixation are shut down by exogeneous nitrogen. “Our work is aimed at counteracting this effect and giving nature a helping hand. Our plan is to specifically select microbes that can provide plants with large amounts of nitrogen, allowing reduced fertilizer use.”
Currently, around half of the world’s population is fed by food produced using synthetic fertilizers.
However, the bacteria also need to possess other characteristics. They need to be easy to engineer in a lab while also being capable of being produced on an industrial scale. They also need to be able to be applied to seed. “That means that these microbes have to survive for long periods without water,” explains Barbier. The idea is to apply them to seeds as a coating that would only become active when the seeds germinate.
Once the Joyn Bio team has identified some promising bacteria, that’s when things will start to get interesting because what works in the lab doesn’t always work out in the field. “Exactly how plant roots interact with the microbiome – the soil bacteria in their immediate environment – is still largely unknown,” says Barbier. The sort of symbiosis enjoyed by legumes and their bacterial companions has evolved over millions of years. “If we’re going to solve the major challenges of our century, we won’t have anywhere near that much time,” explains Miille. “We have to boldly strike out in completely new directions to have a chance of success.”