Bacteria from the roots of a corn plant can break the bonds between two nitrogen atoms. Now that this has been proven, such bacteria could be used to minimize the use of nitrogen fertilizers in agriculture.
This should be apparent from new research results that were published in the scientific journal of the American Chemical Society.
The bacteria have been developed and are being commercialized by the agricultural start-up Organic Pivot from Berkeley in the US. They fertilize the soil more sustainably than fertilizers and are the first genetically engineered bacteria developed for growing cereal crops such as maize.
Plants need nitrogen to grow efficiently. Every year, farmers worldwide use more than 100 million tons of nitrogen fertilizers: ammonia, nitrates or other nitrogenous compounds. More than half disappears into the environment.
This leaching is a notorious source of water and air pollution and a threat to natural biodiversity as we know in the Netherlands, because that problem is the core of the nitrogen crisis that has been holding the Netherlands hostage since the spring of 2019.
Plants can also get nitrogen from naturally occurring soil bacteria that extract nitrogen from the atmosphere. This process is called biological nitrogen fixation. Nitrogen in gaseous form (N2) is abundant in the air, but because the molecule is extremely stable, plants can2 use only after it has broken down. Using an enzyme called nitrogenase, soil microbes cleave the triple bonds that make up N2hold molecules together and help convert them into compounds that plant roots can absorb. Bacteria that work with legumes – such as lentils, soybeans and peanuts – are fairly efficient at fixing nitrogen, but the bacteria that help grains like corn, rice and wheat develop are less so.
Pivot Bio wanted to create a microorganism that provides nitrogen to the plant with the same reliability as a synthetic fertilizer. The company developed it by starting from an isolate of the soil bacteria Klebsiella variicola which selectively colonizes the outer surface of corn plant roots and provides biological nitrogen fixation. Normally, the microbe suppresses its ability to carry out this process once nitrogen has already been fixed. Pivot Bio deleted one of the two genes that control this mechanism and modified the genome so that the nitrogen-fixing ability does not cease. This allows farmers to replace some of their fertilizer use with the genetically modified microbe, which fixes more than a hundred times as much nitrogen than its natural counterpart. According to Pivot Bio It’s “a relatively simple technical change” but the modified microbes still can’t replace all the fertilizers farmers use today. However, they can promise nitrogen-poor bread and pasta. After all, these daily products are made from grain.
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Genetic breakthrough against nitrogen load – Manipulation of bacteria helps reduction of nitrogen fertilizer in grain production – Foodlog