A collection of genes has been transferred into plant-colonising bacteria allowing them to draw nitrogen and turn it into ammonia in a process that scientists say could help farmers use less man-made fertilisers to grow crops like wheat and corn.
The research helps share a symbiotic benefit found in legume crops – such as chickpeas and lentils – which farmers have relied on for centuries to naturally enrich the soil.
Legume crops require significantly less fertiliser than other crops, because they’ve developed a symbiotic relationship with bacteria that grow within their root tissues. These bacteria convert nitrogen gas to ammonia through a process called biological nitrogen fixation.
Bacteria take nitrogen from the air and convert it into ammonia for the plants, which use it for energy to grow. The plants in turn provide carbon and other nutrients to the microbes.
To work symbiotically, legumes and microbes have evolved to release signals that each can understand. The plants give off chemicals that signal to the bacteria when they need fixed nitrogen. The bacteria produce similar signals to let the plants know when they need carbon.
“There’s a growing interest in reducing the amount of fertiliser used in agriculture because it’s expensive, has negative environmental impacts, and takes a lot of energy to make,” said John Peters, Director of WSU’s Institute of Biological Chemistry and a co-author on the paper.
“There’s a huge benefit to developing ways to increase the contributions of biological nitrogen fixation for crop production around the world.”
Reducing fertiliser
To develop a synthetic method for this symbiosis between other bacteria and crops, scientists worked to determine the groups of genes in bacteria that enable nitrogen fixing, then add those gene groups into other bacteria.
“This is just one step, although a large step, on the road to figuring out how to promote increasing contribution of biological nitrogen fixation for crop production,” Peters said.
Peters and WSU are co-leads on the overall project with his colleague Philip Poole at the University of Oxford in the UK.
Reducing fertiliser requirements could have massive impacts on food availability, energy use and agriculture costs all over the world. Fertilisers are too expensive for many farmers around the world. Without them, many nutritionally valuable foods won’t grow in many areas due to nitrogen-poor soil.
“This project is aimed at increasing food production and helping feed the world,” Peters said. “Transforming food production to work without nitrogen-based fertilisers could be a huge development in underdeveloped countries. Adding these microbes would be like pouring kombucha on roots.”
Peters’ lab specialises in studying metabolic processes in bacteria, or how they create and use energy. His lab provided a blueprint for how nitrogen fixation works in different organisms. Then his co-authors, synthetic biologists at the Massachusetts Institute of Technology, can create the mechanisms that microbes and plants will need.
“This is such a complex and wide-spread challenge it really takes a large team with varied areas of expertise to solve,” Peters said. “But if we succeed, the reward could be huge for the entire planet.”
