It is a special photosynthetic mechanism that characterizes the single-celled organism found in algal blooms. What cellular mechanisms in single-celled marine algae are responsible for initiating toxic algal blooms? Microbiologist Prof. from Germany’s University of Oldenburg. Dr. A research team led by Ralf Rabus has performed the first detailed analysis of the unusual cell biology of Prorocentrum. chordatea globally widespread species of the dinoflagellate group using both advanced microscopy and proteomic approaches.

As reported by a research team in a scientific journal Plant Physiology The photosynthesis process in these microorganisms is organized in an unusual configuration that may help them better adapt to changing light conditions in the oceans. The results of the study may contribute to a better understanding of the occurrence of harmful algal blooms, which may become more frequent due to climate change.

Dinoflagellates are important organisms in both marine and freshwater ecosystems. These single-celled organisms make up a significant portion of the free-living phytoplankton that forms the basis of the food web in oceans and lakes. Some species including Prorocentrum chordatecan grow in warm, nutrient-rich waters and create harmful algal blooms.

“We studied this organism because, despite its ecological importance, its cell biology and metabolic physiology are still not fully understood,” Rabus said. said. In addition to studying the photosynthesis of microalgae, the researchers also investigated the structure of cell nuclei and their response to heat stress in collaboration with teams from the universities of Hannover, Braunschweig and Munich, and reported the results in two more recently published papers. .

Advanced imaging techniques reveal unique cellular structures

Using a powerful focused ion beam scanning electron microscope at the Ludwig-Maximilians-University of Munich, Rabus and a team led by lead author Jana Kalvelage from the Institute of Chemistry and Biology of the Marine Environment (ICBM) were able to reconstruct three of them. Dimensional architecture of chloroplasts in which photosynthesis occurs. The scientists were able to create nearly 600 layers of images of a single algal cell and then combine these sections to create a three-dimensional, high-resolution spatial image of single-celled, oval-shaped organisms; these are usually 10 to 20 pieces. one part per thousand. millimeters long. Analysis showed that Prorocentrum chordate There is a single barrel-shaped chloroplast that takes up 40 percent of the cell volume.

Later, proteomic (protein) analysis revealed distinct differences between the photosynthetic apparatus of microalgae and the photosynthetic apparatus of microalgae. Arabidopsis thalianaIt is a well-studied model plant in genetic studies. In both species, photosynthesis occurs in complex protein structures embedded in the branched membrane system of the chloroplast.

However, Prorocentrum chordate The team observed that the conversion of solar energy into biochemical energy occurs in a large structure consisting of numerous proteins known as a “megacomplex”, while in the chloroplasts of plant species the various stages of photosynthesis occur in spatially separated structures. The team also reported: Cordatum It uses many different pigment-binding proteins to capture solar energy efficiently. “This diversity is a specific adaptation to the changing light conditions to which the organism is exposed in the oceans,” Rabus explained.

A study of genetic complexity and adaptability

Two other studies published last year highlight the unusual biology of microalgae: In the first, a German-Australian team that also included ICBM researchers found that the organisms have a very large genome containing twice as many base pairs as humans. The team also found that algae changed their metabolism and slowed their growth rate in response to heat stress. In the second publication, the team led by Rabus and Kalvelage defined the cell nucleus in more detail and reported: Cordatum It has 62 chromosomes; this is an unusually large number, filling almost the entire cell nucleus. The team noted that the function of a significant portion of the nuclear proteins identified by the researchers is currently unknown.

“We investigated how these important microalgae work at the molecular level. These findings lay the foundation for a better understanding of their role in the environment.” Rabus emphasized. He explained that further research could provide answers to questions such as how the body’s metabolism responds to other stressors and why the species is able to adapt to a wide range of environmental conditions, from tropical to temperate conditions.