Close cooperation in the cell
You and I, like all complex multicellular organisms, owe our existence to endosymbiosis. Andwat? Just like plants and fungi, we are eukaryotes. This means that the genetic material (DNA) is located in the cell nucleus, and that cells also contain specialized structures with a specific task. These structures are called organelles, by analogy with the role of organs at the level of the entire organism. Some of these organelles are the result of endosymbiosis.
All eukaryotes contain mitochondria, organelles specialized in converting energy in food into energy that can be used in all types of processes in the cell. These energy factories contain their own DNA and reproduce in a way strongly reminiscent of bacterial cell division.
This led biologist Lynn Margulis to suspect in the 1960s that mitochondria arose after a distant, single-celled ancestor ingested aerobic (oxygen-loving) bacteria without ingesting them about two billion years ago. Instead, the bacteria and the host cell become partners that can no longer survive without each other, i.e., endosymbionts.
Somewhat later in evolutionary history, other eukaryotes were also able to enter into such an endosymbiotic partnership with photosynthetic bacteria. This second fusion gave rise to the chloroplast, the green organelle responsible for photosynthesis in plants and algae.
The article is in Reports on the discovery of a new organelle in the unicellular alga Braarudosphaera bigelowii. Researchers now see sufficient evidence that this organelle is the result of endosymbiosis that is estimated to be 100 million years old. This shows that this form of close cooperation has occurred before, and even relatively recently in the long evolutionary history of life on Earth. The discovered organelle was named nitroplast, which enables the algae to produce usable nitrogen themselves.
The importance of nitrogen fixation
Nitrogen is an essential element for all life on Earth. It's not only found in proteins, it's also literally in our DNA. There is no shortage of nitrogen on Earth, because approximately 80% of our atmosphere consists of nitrogen gas (N2). However, nitrogen gas is relatively inert and not directly usable by living organisms. It first had to be converted to reactive form. This happens in nature in a limited number of ways. One important method is nitrogen fixation by bacteria. Some bacteria are able to convert nitrogen gas into reduced nitrogen in the form of ammonium (NH4+). This nitrogen becomes accessible to plants, among other things, that need it to grow.
Some of these bacteria live in symbiosis with certain plants. The leguminous plant family, which includes a number of important agricultural crops such as soy, chickpeas, beans and clover, enters into such a partnership with nitrogen-fixing bacteria belonging to the genus Rhizobium. These bacteria live in small nodules hanging from the plant's roots. In exchange for sugars, they provide the plant with usable nitrogen.
This special ability of leguminous plants has long been known to farmers. For example, it is beneficial for soil fertility to alternate the cultivation of cereals with the cultivation of legumes, which add more nitrogen to the soil. The ancient Maya practiced mixed agriculture of squash, corn, and beans, the latter being responsible for nitrogen fixation.
The importance of leguminous plants for soil fertility has been neglected since the discovery of fertilizers by German chemists Fritz Haber and Karl Bosch in the early twentieth century. The Haber-Bosch process for industrial production of ammonia was in fact the basis for massive population growth in the last century, and remains indispensable to the global food supply today. However, there are some drawbacks to this process: it is an energy-intensive process, and the ease with which we ourselves introduce reactive nitrogen into circulation contributes to ongoing environmental problems such as eutrophication of waterways and eutrophication of nitrogen deposition in nature reserves.
What year Prarodosphaera bigeloi What makes the nitroblast unique is that it is the first eukaryotic organism that we know of to fix nitrogen itself. Not through loose cooperation with bacteria, but through a specialized organelle, the nitroplast. Algae can produce its own fertilizer. Imagine if there were agricultural crops that possessed this supernatural power!
The holy grail of plant biotechnology
We have been modifying crops since we began agriculture in the Near East about 12,000 years ago. Firstly by selecting seeds of plants with desirable characteristics only by sight, but since the last century also with specific knowledge of the plant's DNA, and with biotechnological techniques to specifically interfere with this DNA. While many of these breeding efforts focus on pest resistance, taste, or nutritional characteristics, there are two goals that—with a bit of exaggeration—could be considered the holy grail of plant biotechnology. The first relates to making the photosynthesis process itself more efficient, through the enzyme responsible for sequestering carbon dioxide2RuBisCO, more efficient.
Researchers from the University of Illinois, among others, have already succeeded in making tobacco plants 40% stronger. The second challenge is that non-legume crops such as cereal crops (wheat, barley, rice, maize, millet) lack nitrogen. One possible approach is to allow these cereal crops to work with bacteria in the soil, just as leguminous plants do.
However, the discovery of nitroplasts opens a new possibility: creating crops that can provide their own reactive nitrogen. This may not be easy, because there is more to it than, for example, the precise cutting and pasting of DNA as is the case with the CRISPR-Cas9 system. With multicellular plants that are quite similar to them Prarodosphaera bigeloi If we fix nitrogen ourselves, we are entering the field of synthetic biology, a branch of biotechnology that focuses on (re)designing the cell itself. Therefore, it is likely that nitrogen fixing plants will not be available in the near future.
Perhaps this can be done faster in single-celled algae, which also offers new horizons. You can grow algae in a closed, controlled environment, unlike field crops. Algae are also becoming increasingly popular as an alternative source of protein for human nutrition. Proteins contain a lot of nitrogen. If one succeeds in destroying single-celled algae e.g Spirulina to Chlorella Using nitroplasts, this can provide a dramatic increase in the efficiency of using algae in the protein transfer process.
