An article published in the journal “Cell Host & Microbe” reports the results of a study on the widespread symbiosis between predatory protists and bacteria related to species that are pathogenic to various animal species and sometimes to humans. A team of researchers led by scientists from the Marine Biological Laboratory (MBL) conducted a series of analyses on water samples collected at the surface of the Pacific Ocean, the Caribbean Sea, and the North Atlantic and identified protists that have predatory habits that eat some species of bacteria but are in symbiosis with other species. The results suggest a long and complex history of relationships that sometimes are symbiosis and sometimes are parasitism by bacteria with animals and choanoflagellates, the closest relatives of animals among eukaryotes.
Protists are a very heterogeneous group of eukaryotic organisms that are not animals, plants or fungi. The taxonomic classification has changed in ways that sometimes are radical over the last century and recent developments in genetic techniques are offering a lot of information. However, the remarkable diversity existing in the groups of protists was confirmed at the genetic level as well and that offered few answers and many new questions about the relationships existing between the various groups of protists and with the other kingdoms of eukaryotes. For these reasons, even in scientific articles, researchers continue to speak of protists but it’s a term now used for convenience due to its now consolidated use, while scientific rigor concerns specific groups of these organisms.
The diversity of protists is the reason why they are present in very different ways in ecosystems. This research focused on ocean ecosystems, where there are species of organisms included in the large group of protists that have predatory behaviors. These protists feed on phytoplankton and bacteria and in turn constitute food for other marine animals.
Precisely thanks to the advanced genetic techniques that have become available, it’s been possible to conduct a long research that took years to collect samples from the surface of ocean waters, analyze them, and study the results. The Marine Biological Laboratory (MBL) is dedicated to scientific research that aims to explore and understand biodiversity and the environment, which includes having some of its researchers as guides for this study.
We’re used to receiving new information about the microorganisms that live in symbiosis with us, especially in our intestines, where they form a real ecosystem. It may seem strange that organisms as tiny as protists could have something similar, yet there are species that live in symbiosis with bacteria. The protists examined in this research are among the smallest among those that live in the oceans, with lengths between 2 and 5 microns.
These protists live in symbiosis with a few bacteria, but this can still be interesting when they belong to species related to pathogens that practice parasitism against animal species and in some cases humans. The genetic study of the various groups of bacteria can provide new information that is useful for understanding the evolution of symbiosis and parasitism. This also includes a better understanding of infection vectors with medical implications that could make a difference in the event of a risk of epidemics.
Medical research connected with the symbiosis between protists and bacteria could be important, but that’s also true for research connected to ocean ecosystems. In a time when many ecosystems are suffering due to climate change and pollution, understanding the role of different groups of organisms within them is more relevant than ever, and in many cases, microorganisms can play key roles.
