Arrested! Marine algae and bacteria with a special property came into contact with each other. The seaweed then absorbed the bacteria and slowly began transforming the bacteria into a permanent part of itself, called an organelle. In this way, marine algae took over this special property of bacteria. Thus it gained an evolutionary advantage. The transformation from bacteria to organelle is still ongoing.
American and Japanese researchers Describe this process This Thursday Sciences. This is the first time that a complex, single-celled organism (marine algae) has been found to possess an organelle through which it can extract nitrogen from water and convert it into a usable form. This so-called nitrogen fixation is a crucial process for life on Earth. Until now, the idea was that only simple, single-celled organisms could do this. They take nitrogen from the air, or water, and convert it into a form that other organisms can absorb. Nitrogen is an important building material for plants and animals, including the production of proteins.
Divided into three groups
“This research is a really beautiful story,” answers Corne Pieterse, professor of plant-microbe interactions at Utrecht University and not involved in the study. This is also said by Carlos Santana Molina, a bioinformatics specialist at the Royal Netherlands Institute for Marine Research. “For evolutionary biology, this is really remarkable.”
Life on Earth is roughly divided into three groups: bacteria, archaea, and eukaryotes. The last group includes plants, animals, fungi, and some single-celled organisms. They are characterized by the fact that their cells contain a cell nucleus and specialized parts, which are organelles. A well-known example is mitochondria, which are the energy factories of the cell.
“Mitochondria were once free-living bacteria,” Pieterse says. They lived in symbiosis with primitive eukaryotic cells. Both organisms evolved at some point into a single cell, with the mitochondria turning into an organelle. “This integration began about 2.5 billion years ago,” Santana says. Something similar applies to chloroplasts, which are the green plastids in plant cells that capture solar energy and carbon dioxide.2 To carbon sources for plants. In it now Sciences The described organelle is the third example of a bacterium that has been taken up by a eukaryote and converted into an organelle. This is the first example of a eukaryote fixing nitrogen. Researchers call the organelle “nitroblast.” “We estimate that the transformation process began about 100 million years ago,” says Jonathan Zahr, coordinating author of the study.
The researchers concluded, based on a number of observations, that the ingested bacteria have already transformed to such an extent that you can talk about an organelle. Compared to their closest living relatives, bacteria have already lost much of their DNA. In addition, the division of bacteria coincides with the division of marine algae. These are important properties to be able to talk about the organelle. Santana noticed something else. Some marine algae proteins that first served in plastids – the organelles in which special chemical compounds such as pigments are made – have been given a new purpose and are now being sent to the plastids.
The study authors expect the nitroblast transformation to continue for some time. “The mitochondria and chloroplasts have lost a lot of their original DNA,” Zahr says. “We have not yet been able to identify any genetic exchange between the nitroblast and the host.”
“By following the further evolution of marine algae and netroplasts, we may also be able to learn more about the evolution of organelles in general,” says Santana, who herself researches the early evolution of metabolism in eukaryotes.
marine algae (Prarodosphaera bigeloiZahr says that this type of fish has so far only been caught from Japanese coastal waters. “It took us many years to grow them in the laboratory.” But DNA from mutant bacteria has been found all over the world. “Also in Danish waters.”
Pieterse says the research is also interesting for plant breeders. “They have been trying for years to integrate the full molecular machinery of nitrogen fixation from bacteria into plants.” But that hasn't happened yet. “Nitroplast may provide new insights.”
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