Kategorie: News
Researchers detect large numbers of dormant bacteria in the deep biosphere
A study of marine sediments from around the world shows that dormant bacterial endospores make up a significant proportion of total microbial biomass. For the first time, researchers have determined their number for a study. Now the results of Dr. Lars Wörmer from the MARUM Center for Marine Environmental Sciences at the University of Bremen and his co-authors in the journal Science Advances.
Marine sediments host a large mass of microorganisms, including endospores, resistant, dormant bacteria belonging to the group of Firmicutes bacteria - and they are true survivors. They are able to switch from rest to vital mode as soon as the conditions in their habitat allow it. Researchers have now numerically determined the cells for the first time.
The goal of the team around Lars Wörmer was to use the data to cover the diversity of systems in order to gain a global understanding of the occurrence of endospores. They evaluated sediment samples from all parts of the world and different depths.
It has been known since the 1990s that the deep-sea is not only a place of wasteland, but that there is also life in the marine sediments. Since then researchers have been working to understand how the life of organisms works in depth, in a hostile and nutrient-poor place. The deeper in the seabed, the more adverse the circumstances: the temperature rises, there are hardly any sources of energy. From a depth of about 25 meters below the seabed, there are more endospores than other living cells. As the depth increases, so does the number of dormant cells. However, it is unclear whether the position in the seafloor also gives information about the geological age, or whether the endospores formed sometime during the deposition. "We know the age of the deposits," says Lars Wörmer, "but do not know whether the endospores are just as old."
To detect the spores, the researchers have used the biomarker dipicolinic acid (DPA). DPA stabilizes the spore. If the cells either die or reawaken, DPA is released, so it is no longer detectable. Researchers have searched specifically for DPA in more than 300 marine sediment samples collected between 2002 and 2015 on a total of 15 ship expeditions. The biomarker has been known since the 1960s, however, a suitable analysis for endospores in sediments was developed only 50 years later.
The ecological role of endospores in their habitat is not yet clear. The researchers suspect that the older endospores exist as a kind of seed bank in depth and preserve the genetic diversity here - until they meet a more favorable living environment and reactivate. This is precisely what makes Lars Wörmer's fascination with dealing with the deep biosphere. "Sometimes you do not even know what is hidden in the ocean sediments - and why." In the future, he and colleagues would have to deal with survival forms, but also with their wake-up mechanisms.
Link to the study: advances.sciencemag.org/content/5/2/eaav1024.