How do cyanobacteria manage to take advantage of glucose?

Marine cyanobacteria are the most abundant photosynthetic organisms on Earth and are responsible for producing much of the oxygen we breathe. Although their main source of energy is obtained through photosynthesis, a process with which they convert carbon dioxide (CO2) from the atmosphere into organic matter, depending on certain circumstances they are also capable of directly capturing organic substances from the environment, such as glucose, and assimilate them as an energy source. That is why they are considered mixotrophic organisms, since they have a mixed way of feeding (light and organic matter).

With the aim of knowing those certain circumstances that favor cyanobacteria directly uptake organic substances, the research group “Adaptations in the metabolism of nitrogen and carbon in marine cyanobacteria”, from the University of Córdoba (UCO) in Spain, has carried out several investigations that allow a better understanding of how these organisms assimilate and use glucose, which is the most abundant organic compound in nature.

Thus, in a study published in the academic journal Microbiology Spectrum, the team has seen that the ability to uptake glucose and its effects on metabolism are different between different strains of Prochlorococcus and Synechococcus, which are the two main genera of cyanobacteria that exist. . That is to say, there are some cyanobacteria that are more efficient when it comes to capturing glucose and the use they make of it can also be different since “marine cyanobacteria in the ocean are capable of shaping their metabolism depending on the availability of glucose.” glucose”, explains José Manuel García Fernández, from the research group.

Now, one thing is the assimilation of glucose (that is, how they use this organic matter), and another is how they manage to capture it. To do this they use proteins called transporters. These proteins are responsible for identifying glucose in the environment and introducing it into the interior of the cell. In a study published in the academic journal BBA Bioenergetics with the collaboration of the New University of Lisbon in Portugal, the team has managed to accurately identify the structure and functions of the Prochlorococcus glucose transporter, which stands out for being able to identify small amounts of glucose around you. “Future studies,” explains García Fernández, “will make it possible to answer the question of what specific parts of this transporter are responsible for its having this capacity.”

From left to right, María del Carmen Muñoz Marín, Jesús Díez, José Manuel García Fernández, José Ángel Moreno Cabezuelo, Guadalupe Gómez and Antonio López Lozano, from the Group Adaptations in the metabolism of nitrogen and carbon in marine cyanobacteria, attached to the UCO . (Photo: UCO)

In addition, in research carried out in collaboration with the Universities of Hawaii and Arizona in the United States, published in the academic journal Microbiology Spectrum and in which they have analyzed natural samples during an oceanographic campaign in Hawaii, the team has added three more characteristics to the relationship of Prochlorococcus with glucose. First, that glucose transport is greater during the day than at night thanks to the availability of light. Second, that glucose uptake follows a different circadian cycle than other bacteria living in the same area of ​​the ocean. And finally, the team discovered differences in glucose metabolism between surface and depth cyanobacteria.

This entire process of glucose assimilation is essential for some cyanobacteria and gives them advantages over their competition: they save energy (since it takes more effort to transform CO2 into organic matter than to feed directly on it) and they remove organic matter from other competing microorganisms. that are around you. In addition, although the main source of energy for cyanobacteria is sunlight, many live in deep areas where no light reaches, so it is essential for them to capture organic matter to survive. This has recently been demonstrated by researchers from the University of Haifa (Israel), in a study that UCO professor María del Carmen Muñoz Marín reviewed for the academic journal Nature Microbiology. (Source: UCO)