How does amoeba multiply

: Amoebas: slimy quick-change artists

The being behaves like an alien from a distant world. Dictyostelium discoideum it is said and is one of the types of slime mold. It usually lives as a single cell in the upper humus layer of forest soils. The amoeba crawls around on its own, feeds on bacteria and multiplies through cell nucleus division. However, if it does not find enough food, it becomes sociable. It emits a chemical distress signal that spreads like waves and causes its fellow species to do the same.

As soon as the messenger substance reaches a certain concentration, the amoebas flow towards each other and form aggregates of up to 100,000 cells. The resulting multicellular cells, known as "slugs" because they look like tiny nudibranchs, react to temperature and light and start looking for a new, better location. When they reach their destination, they change shape again. The social amoeba becomes a plant-like structure. About 20 percent of the cells form a one to two millimeter long stalk, the remaining 80 percent transform into a fruiting body made from amoeba spores.

Amoebas as model organisms

The spore cells survive the starvation phase - there is no happy ending for the stem cells: "After they have lifted the spore mass so that it can spread better, they die, while the distributed spores live again as unicellular cells." , says Sascha Thewes, microbiologist at the Free University (FU) Berlin. He has been working intensively on the social amoeba for years. Like many other scientists around the world. Thewes is a member of the international research network dictyBase, which annually organizes a so-called dicty conference that only deals with slime mold. The conference has existed since 1981. This year's conference - with around 110 participants - took place last week in Potsdam.

Dictyostelium discoideum was discovered and isolated in 1935 by the US microbiologist Kenneth Bryan Raper. Since then, the amoeba has become an important model organism in research, ”says Sascha Theses, who helped organize this year's conference. Microbiologists, biophysicists, cell biologists and physicians are researching the social amoeba. Above all, the selfless behavior of the stem cells, which sacrifice themselves for the common good, fascinates many researchers. Based on the special life cycle of Dictyostelium discoideum many interesting scientific observations can be made. For example, those who take a close look at them in the laboratory can follow the transition from single to multicellular cells or find out why different cell types can develop from the same cell. Fundamental processes within cells can also be studied - from division through the construction of their structures to death.

"The knowledge gained is very valuable because the genetic material of the social amoeba and the cellular processes that take place in it are similar to those of higher living beings such as humans in many respects," says Sascha Thewes. Because the amoeba can multiply and genetically change easily in the laboratory, researchers can experiment with it in a targeted manner and ask a wide variety of questions. Among other things, how cells deal with pathogens or how defects in the genetic material affect their development.

Research on Alzheimer's and Parkinson's

A small selection of the latest research projects is presented year after year at the Dicty conference. This time, researchers included, based on Dictyostelium discoideum examine how cells move or what role messenger substances play in their development. The microorganism is also used as a model for researching cellular defense mechanisms against diseases.

“We are investigating how the social amoeba interact with fungi that are pathogenic to humans, such as yeast Candida albicans bypass ”, Sascha Thewes explains the approach of the working group to which he belongs at the Institute for Biology and Microbiology at the FU. In this way one could possibly gain clues for anti-fungal treatment of people. Because the amoeba resembled human immune phagocytes in many ways.

Other lectures dealt with neurological diseases such as Alzheimer's and Parkinson's: “Certain genes play a role in their development, some of which are also involved Dictyostelium discoideum there, ”says Thewes. This is why the organism can be used to research the normal function of these genes and to draw conclusions about how they mutate and why they make sick in their faulty form.