Microorganisms skip the process of releasing oxygen, absorbing carbon dioxide during photosynthesis

A surprising discovery discovered by scientists at the Carngie Institute has brought a new step for research on capital photosynthesis, thought to be one of the most important biological processes on Earth.

Thanks to plant photosynthesis, algae and certain types of bacteria provide energy for most living organisms by producing food from sunlight. During photosynthesis, these organisms release oxygen and absorb carbon dioxide.

However, two studies conducted by Arthur Grossman and colleagues show that some marine organisms have evolved a way of photosynthesis that does not follow the above rule. They produce a significant amount of energy without absorbing carbon dioxide or releasing oxygen. These two studies were published in Biochimica et Biophysica Acta and Limnology and Oceanography. Arthur Grossman's discovery not only shocked scientists' basic understanding of photosynthesis, but it could also help explain why marine microorganisms make gas Carbon dioxide in the atmosphere increases.

Grossman and his team studied photosynthesis in marine bacteria Synechococcus - a type of photosynthetic bacterium that has a common name cyanobacteria (formerly known as green algae). These unicellular organisms dominate all plankton in the oceans around the world, they are also important contributors to global basic productivity.

Grossman and his colleagues wanted to find out how Synechococcus grows in iron-poor waters that account for most of the oceans; While normal photosynthesis requires high iron participation. Others argue that oxygen has a potential role in receiving electrons from photosynthetic devices to replace carbon dioxide. However, Grossman's team has shown that this activity is significant when carried out in poor nutrient waters that cover half of the ocean.

Sausage-shaped cells are bacteria of Synechococcus and silk fibers are actually green bacteria without sulfur. (Photo: Richard W. Castenholz, University of Oregon)

Grossman said: 'It is more or less likely that Synechococcus bacteria in nutrient-poor oceans have also solved the problem with iron by bypassing the normal photosynthesis process. They ignored the steps involved in iron during photosynthesis. And those are the steps that carbon dioxide is absorbed from the atmosphere. '

Shaun Bailey, a postdoctoral researcher working on the project, said: 'We soon realized the differences in Synechococcus. Absorption of carbon dioxide and photosynthetic activity in this bacterium does not fit together. So we know that there is something not carbon dioxide being used in photosynthesis. And indeed it is oxygen. ' The researchers identified an enzyme involved in this process, PTOX (plastoquinol terminal oxidase). They also stressed that new photosynthesis should be considered in understanding the basic productivity of ocean ecosystems.

In the normal photosynthesis process, light energy dissolves water molecules, releases oxygen and provides electrons used to fix carbon dioxide taken from the atmosphere and creates energy-rich molecules - wallet like sugar. For the newly discovered process, a large portion of these electrons are not used to fix carbon dioxide, instead they bind water molecules together, resulting in less oxygen during photosynthesis.

Bailey said: 'It seems that these organisms are working on a process that turns water into water ineffective under light. But that's not true because this unusual cycle is also a way to use light to generate energy while still protecting the photosynthetic machinery from possible damage caused by absorption of light. shining'.

Generating energy from the process of turning water into water under the influence of light plays an essential role because cyanobacteria use energy to capture the meager supply of nutrients in their habitats. This new phenomenon has been proven by nature researcher Kate Mackey. Kate Mackey conducted direct photosynthesis studies on research samples from the Pacific and Atlantic.

Mackey said: 'The nutrient-poor, iron-poor environment accounts for about half of the world's oceans. This suggests that a large proportion of the Earth's surface is used for photosynthesis. Our findings show that this unusual cycle occurs in the two main ocean basins; At the same time it also indicates that the vital energy source from sunlight does not work simultaneously with the fixation of carbon dioxide during photosynthesis. That means that photosynthetic organisms in the ocean absorb less carbon dioxide from the atmosphere than we think . '

Joe Berry of the Global Ecology Department - Carnegie Institution said: 'This discovery brings changes in our perception of photosynthesis in organisms that live in vast, nutrient-poor areas. We still think that, like higher plants, the goal of photosynthesis is to produce carbohydrates from carbon dioxide and store them for future use as an energy source for some of the cell functions. or to develop. But now we know some organisms have ignored this complicated process. They use minimal light to power cell cycles through a simpler, more economical photosynthetic machine when the environment lacks nutrients such as iron. We don't know the meaning of this phenomenon well, but it will certainly change the way we understand the optical framework of photosynthetic pigments in the ocean and how we build energy models. ocean productivity '.

Wolf Frommer, director of the Carnegie Institution's Department of Plant Biology, agrees with the leaps and bounds of discovery.'If we think that we have understood the process of photosynthesis, this study has shown that there are many things we need to learn about these basic physiological processes. Research by Grossman's lab, along with previous evidence suggested by Greg Vanlerberghe of the University of Toronto, proved that the gene encoding the PTOX enzyme seems to be widespread in the cyanobacterial oceanic bacteria group. It will create a solid foundation for building a basic ocean productivity model. '

The authors of the study include: Shaun Bailey, Anastasios Melis, Katherine RM Mackey, Pierre Cardol, Giovanni Finazzi, Gert van Dijken, Gry M Berg, Kevin R Arrigo, Jeff Shrager, Arthur R Grossman.