Protists are microorganisms that, unlike bacteria and archaea, have a cell nucleus, that is, they belong to the super kingdom of eukaryotes. They are divided into autotrophic (capable of synthesizing organic substances from inorganic ones) and protozoa, they are heterotrophic protists, that is, they need organic matter from the outside to support life. Scientists wanted to find out which protists inhabit the soil in different parts of the world in order to later more accurately determine what role these microorganisms play in various ecosystems. The results of the study are published in the journal Science Advances.
Even small soil samples contain a huge amount of microorganisms. Protists reproduce very quickly. Scientists believe they are much more responsive to changes in their habitat than larger life forms.
These creatures move with the help of tiny flagella or cilia hairs. They inhabit almost any environment, including ourselves. Some of them are dangerous: they cause, for example, sleeping sickness or malaria, while others are neutral. The representatives of this kingdom living in the soil make up a very large part of the biomass and play a significant role in the sustainability of the ecosystem.
Previously, it was not possible to effectively identify millions of these creatures in the soil. The new work used a newly developed technology to classify protists based on their genetic code. The team sequenced 18S ribosomal RNA, studied from soil samples from all six continents, to better understand what is happening inside the soil.
It turned out that most of the protists they identified spend their lives as Pac-Man, a popular character in the arcade game. Moving continuously inside the soil, they look for smaller bacteria and consume them, dodging larger and more aggressive attacking microorganisms. But there are also a number of other types. So, in tropical soils, there were more protist-parasites living inside other organisms. In desert soils, there are also enough autotrophic protists - capable of photosynthesis and using sunlight directly as an energy source.
The team found that the best predictor of what types of protists will appear in a soil sample is the annual rainfall at the site where it was taken. This may seem intuitive, since protists are dependent on the movement of water. However, in fact, here they are very different from bacteria or fungi - they are more affected by the acidity of the soil.
"Soils are home to an amazing variety of organisms that we are just beginning to understand," says author Ben Turner, a research fellow at the Smithsonian Institute for Tropical Research in Panama.
Besides the fun fact about microorganisms and their lives, the work could seriously advance microbiological research. The methods tested by scientists will be useful for both agriculture and medicine.