Two researchers have identified a new organelle that allows a type of algae to fix nitrogen from the air. The discovery challenges a long-standing rule of biology. It could offer insights for future agricultural innovations.
Jon Zehr, an oceanographer, began searching for unknown nitrogen-fixing bacteria in the 1990s by testing seawater samples for the nitrogenase gene. He repeatedly detected genetic traces but found no matching organisms under the microscope across locations from Hawaii to the Arctic.
Kyoko Hagino, an algae specialist in Japan, independently studied Braarudosphaera bigelowii and noticed an unexplained black dot inside the cells. Genetic testing later confirmed the dot as the bacteria Zehr had sought.
Their collaboration revealed that the bacteria had evolved into an organelle named the nitroplast. The algae and bacteria divide together and share genes in a system previously seen only in mitochondria and chloroplasts.
Zehr and Hagino noted that the finding shows complex organisms can now fix nitrogen. They cautioned that engineering similar traits into crops remains a distant prospect.