Superhero Chloroplasts


This week, I bring you another plant-related article, this time discuss how scientists are trying to upgrade the photosynthetic process in plants.

chloroplast

A chloroplast, which, in the future, could be filled with honeycomb-like structure called carboxysomes

It has been a billion years since an eukaryote ingested a chloroplast and by accident created the essential symbiotic relationship to which we owe all the energy by which we survive. However, the way chloroplasts work hasn’t really changed in all these years, even though the environment has, and its system is quite obsolete. On the other hand, the descendants from the species of the first chloroplast, the cyanobacteria, have really changed their photosynthesis, which is much more efficient than that of chloroplasts.

The main difference between our world and the world a billion years ago, at least for this topic, is CO2 and 02 levels in the atmosphere. Before, there was an enormous amount of carbon dioxide in the atmosphere, which cyanobacteria and chloroplasts could exploit to produce food by photosynthesis. But as plants became more abundant, they absorbed the CO2 and released 02 , giving rise to our current balance of elements in the air. The most favourable conditions for a fast photosynthetic rate are high levels of CO2 in the air but since this is not the case anymore, there is a need for some changes in the organisms themselves. Plants, which have remained mostly unchanged, have reduced their efficiency, whereas cyanobacteria, which have evolved, actually improved it. The key to their success lies in their ability to maintain high levels of CO2 within the cell, thanks to carboxysomes. These are tiny, regularly-shaped compartments that fill the bacteria, and are specialised in maintaining CO2 trapped in them, so there is more of it available for photosynthesis. They even have protein pumps in their membrane which actively pumps CO2 into the cell.

This unique mechanism is what scientists are now trying to copy into a normal plant chloroplast. To do so, they would use genetic engineering: adding genes from the marvelous cyanobacteria to the chloroplasts so they would develop the pumps, which could increase efficiency between 15-25%; an outstanding upgrade. Transferring the carboxysome technology would be a bit more complicated, requiring more genes and the knowledge on how to make the structure itself, which at the moment is lacking.

Still, this innovative improvement offers an immense upgrade, which would sure be useful to farmers and food suppliers, who have found a rapid increase in their customer pool but a slow increase in their yield, a problem which could be remedied if this solution worked.

As always, there is some opposition, arguing that if plants have evolved for millions of years and have never developed a new way for photosynthesis to occur, there must be a reason for a reason, so natured shouldn’t be tinkered with. The pros and cons for this situation are many, and it is a subject which divides the scientific community.

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Life is all about Change


In an experiment in Michigan State University, scientist Richard Lenski started growing a group of E. coli bacteria in 1988. The bacteria have kept reproducing since then, making the incredible amount of more than 50,000 generations. But there is a purpose to this experiment: study evolution and answer a very simple question: Is there an end to evolution?

Lenski grew about 12 different groups of E.coli bacteria in a simple, constant medium. He used bacteria because this type of organism grows and reproduces very quickly and they are fairly easy to manipulate and study. It was important that the environment was kept constant, because any little change could affect the evolutionary process.

After every 500 generations, a sample was taken and frozen, so at some point, a group of bacteria from different generations was put together and their aptitude at surviving compared to each other is be measured.

The results are very surprising and revealing. Every generation, Lenski found, had a minor improvement over the former one. The grandson was always fitter than the grandfather; no matter how many times the experiment was repeated. But this was expected. The news is that, at some point, the improvements were less and less obvious, so even though there were still changes, they weren’t so useful or noticeable with each generation.

E. Coli bacteria

E. Coli bacteria

This is an example of power law, a mathematical term used to describe a sequence that is ever increasing, but the amount by which it grows, decreases.

This information is interesting because, up until now, it was thought that organisms had a limit as to how adapted they could be. This applies only to constant mediums. In the real world, there is always going to be changes, because the environment or the habitat changes all the time, however small the changes are. So the answer to our first question was no. There are always changes around us, so we are always going to be changing. Even if the world stopped changing in every minute detail, we would still be developing new ways in which to be fitter for survival.

Some people say that this could not be applied to humans or other species, but the idea is the same. Just like your parents said, there is always something you can do to be better.