The studies provide a better understanding of how cyanobacteria exploit glucose

Three UCO studies investigate how Earth’s most abundant photosynthetic organisms, marine cyanobacteria, can also obtain energy from organic substances such as 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 through photosynthesis, a process by which they convert CO₂ from the atmosphere to organic matter, depending on certain conditions they are also able to directly capture organic substances from the environment, such as glucose, and assimilate them as a source of energy.

That is why they are considered mixed-trophic organisms, as they have a hybrid way of feeding (light, and organic matter).

Aiming to understand the specific circumstances that allow cyanobacteria to directly capture organic matter, a research group at UCO, Adaptations in the Metabolism of Nitrogen and Carbon in Marine Cyanobacteria, has conducted several studies that shed light on how these organisms assimilate and take up advantage of glucose, which is the most abundant organic compound in nature.

In a study published in the journal Microbiological Spectrumthe team found that the ability to bind glucose and its effects on metabolism are different between different strains of Prochlorococcus and Synechococcus, which are the two main genera of cyanobacteria.

That is, there are some cyanobacteria that are more efficient at capturing glucose, and its use can also be different, as “marine cyanobacteria in the ocean are able to regulate their metabolism depending on the availability of glucose,” explained José. Manuel García Fernández, member of the research team.

Now, it is one thing to assimilate the glucose (that is, how they use this organic matter), and another thing is how they manage to capture it. For this, they use proteins called transporters. These proteins recognize glucose in the environment and bring it into the cell. In an article published in BBA Bioenergeticsin collaboration with the Universidade Nova de Lisboa, the team was able to precisely determine the structure and functions of the Prochlorococcus glucose transporter, which stands out for its ability to recognize small amounts of glucose around it.

“Future studies,” explains García Fernández, “will allow us to answer the question of which specific parts of this transporter are responsible for the existence of this capacity.”

Additionally, in research conducted in collaboration with the University of Hawaii and the University of Arizona, published in Microbiological Spectrumin which they analyzed natural samples during an oceanographic expedition to Hawaii, the team added three more features to the relationship between Prochlorococcus and glucose.

First, they found that glucose transport is greater during the day than at night thanks to the availability of light. Second, glucose uptake follows a different circadian cycle than that of other bacteria living in the same area of ​​the ocean. Finally, the team discovered differences in glucose metabolism between surface and deep cyanobacteria.

This whole process of glucose assimilation is fundamental for some cyanobacteria and creates advantages over their competition: they save energy (since more effort is required to convert CO₂ on organic matter rather than feeding directly on it) and obtaining organic matter from other competing microorganisms around them.

And, although cyanobacteria’s main source of energy is sunlight, many live in deep areas where no light reaches them, so they need to capture organic matter to survive. This has recently been demonstrated by researchers at the University of Haifa (Israel), in an article that UCO professor María del Carmen Muñoz Marín reviewed for Nature Microbiology.