Science / Israeli researchers observed for the first time the "cooperative" reproduction of single-celled creatures

The amoeba "the midwife" is pushed between the "mother" and the "daughter" and pushes them in opposite directions. The reproduction techniques in nature are different and varied, but they can all be divided into sexual reproduction
and asexual reproduction. In sexual reproduction, two partners take part and help each other. Such a thing, so they thought

Marit Sloin, "The Land"

22/03/2001
"Cooperative" division of Amoeba. The "midwife" amoeba is squeezed between the "mother" and the "daughter" and pushes them in opposite directions

Thursday the 22th of Adar 2001, March XNUMX, XNUMX

Science / Israeli researchers observed for the first time the "cooperative" reproduction of single-celled creatures

On the right-the mother amoeba, on the left-the daughter amoeba, and in the middle-the midwife amoeba

By Marit Selvin, the "Eretz"

"Cooperative" division of Amoeba.

The amoeba "the midwife" is pushed between the "mother" and the "daughter" and pushes them in opposite directions. The reproduction techniques in nature are different and varied, but they can all be divided into sexual reproduction
and asexual reproduction. In sexual reproduction, two partners take part and help each other. Such a thing, so far thought, does not happen in asexual reproduction. But a multidisciplinary research team from the Weizmann Institute, studying the culture of amoebae (which is done asexually, through cell division), observed for the first time mutual assistance in the reproduction process in the microscopic world of these single-celled creatures. Their discovery is published today in the journal "Nature".

The amoeba reproduces like this: the amoeba doubles its genetic load, creates two nuclei, begins to swell and in the center a narrow "waist" tightens. This process continues until two almost separate cells are formed, connected by a very narrow passage. At this fateful pre-separation stage, several scenarios are possible. In one, the two cells—the "mother" and the "daughter"—stretch the region connecting them until it breaks; In the other, the "mother" and "daughter" stretch and stretch the junction area, but fail to detach from each other and return to the single cell configuration, which now contains two nuclei. Until now, scientists believed that these two scenarios were the only possible ones, but the researchers from the Weizmann Institute show that there is a third scenario, in which a third amoeba is involved that plays the role of "midwife".

The research was started by Prof. Elisha Mozes from the Department of Physics of Complex Systems. Moses is interested in the physical aspects of the process of cell division. "As a physicist, I was intrigued to know how a cell manages to produce a structure of motor molecules that is able to contract until the section connecting the two cells is cut," says Moses. Mozes told about his research to Prof. David Mirelman, dean of the biochemistry faculty at the institute, who studies, among other things, the properties of amoebas. Mirelman suggested that Moses carry out the research on the amoebas, which reproduce at a faster rate than most cells. Mirelman brought his amoebae to Moses' laboratory, which is equipped with advanced systems for observing, documenting and measuring physical processes taking place in the single cell. The research team, which also included research students Fazit Liberos, Dodo Biron and Dror Sagi, began documenting the dividing amoebas.

"The first thing we wanted to see was how the cells divide. We thought we might be able to get clues from the division method and physical measurements on the motor that shrinks the connection between the two cells," says Biron. The team began documenting the amoebas
that are dividing, and then it turned out, to everyone's surprise, that in quite a few cases, when the "mother" amoeba tries to break away from the "daughter" amoeba, a third amoeba comes to their aid, which is pushed between them, "treads" the "umbilical cord" and pushes the two amoeba in opposite directions until the thread between them He hung up and everyone went their separate ways. "The students told me: 'Come and see how the amoebas come to help each other,'" says Mozes. "It was hard for me to believe that something like this could happen, but the students insisted. We intervened and I lost in the intervention."

"Years ago, the opinion was that every single-celled creature lived completely independently," says Mirelman. "Today it is more and more clear that single cells conduct a dialogue with single cells in their environment. They sense that there are other cells near them through chemical messages that they send. Each has a receptor and also a chemical substance that it sends, and this is how they communicate. We thought that this is also the way you read The dividing amoeba for help." To test the hypothesis, the researchers inserted a microscopic tube into the solution in which the amoebas lived. They brought the tube closer to the separation zone between a pair of amoebae that are in the middle of the division process, and sucked a little of the solution in the zone. In the next step, they dripped a little of this solution at a certain point in the plate where amoebae lived that were not busy dividing. The result: the amoebae were quickly drawn to the infusion area. When the infusion tube was moved, the amoebae began to "chase" it.

"Chemical communication between creatures for the purpose of reproduction is known in nature," says Mirelman. "Insects secrete pheromones and with their help they find their mate. It seems that the desire to reproduce triggers such mechanisms in primitive creatures as well." The researchers believe that the substance with which the dividing amoebas signal and call for help is a unique substance consisting of a combination of a protein segment, a fat segment and sugar. This substance, called LPG, is found on the cell membrane of amoebas. When an amoeba tries to divide, the membrane in the area of ​​division stretches and contracts. These efforts apparently result in the release of some of the LPG from the cell membrane into the food solution in which the amoebas live. As a result, its concentration increases near the "narrow waist" area that needs assistance. Amoebae in the environment sense the material, are attracted to the area and help their companions finish the division process. This hypothesis will be tested by the research team soon.

https://www.hayadan.org.il/BuildaGate4/general2/data_card.php?Cat=~~~310712503~~~59&SiteName=hayadan