Without a central nervous system, how does a single-cell slime mold make an informed decision?
The memory of past events allows us to make more informed decisions about the future. Researchers at the Max Planck Institute for Dynamics and Self-Organization (MPI-DS) and the Technical University of Munich (TUM) have now determined how the slime bacterium polycephalum preserves memories-even though it has no nervous system.
When looking for food or avoiding harmful environments, the ability to store and restore information gives organisms a clear advantage. Traditionally, it has been attributed to organisms with a nervous system.
A new study written by Mirna Kramar (MPI-DS) and Professor Karen Alim (TUM and MPI-DS) raises this point by revealing the amazing ability of highly dynamic single-celled organisms to store and retrieve information about their environment Challenge.
Physarum polycephalum has plagued researchers for decades. This unique organism exists at the crossroads between the kingdom of animals and plants and the kingdom of fungi. It provides insight into the early evolutionary history of eukaryotes. Humans are also eukaryotes.
Its body is a huge single cell, composed of interconnected tubes, forming a complex network. This single amoeba cell may extend several centimeters or even several meters, making it the largest cell on earth in the Guinness Book of World Records.
Network architecture as memory
“It is very exciting to draw a project from a simple experimental observation,” said Karen Allin, head of the MPI-DS Biophysics and Morphogenesis Research Group in Göttingen and Professor of Bionet Theory at the Technical University of Munich. (Karen Alim) said.
When researchers tracked the migration and eating process of organisms, and observed that for a long time after eating, food sources have unique marks on the thicker and thinner tube patterns of the network.
Karen Alim said: “In view of the highly dynamic network reorganization of multi-head sports, the persistence of this imprint has led to the idea that the network architecture itself can serve as a memory of the past.” But they need first. Explain the mechanism of brand formation.
Decisions are guided by memory
To this end, the researchers combined microscopic observations of the adaptability of the tubular network with theoretical models. Contact with food triggers the release of a chemical substance that spreads from the location where the food is found in the entire organism and softens the pipes in the network, thereby redirecting the migration of the entire organism to the food.
First author Mirna Kramar said: “The place where the softening is where the existing imprints of the previous food sources come into play, and the information is also stored and retrieved there.” “Past feeding events are embedded in In the hierarchy of pipe diameters, especially in the arrangement of thick and thin pipes in the network.”
Mirna Kramar added: “For the softening chemicals that are now being transported, the thick pipes in the network are like highways in the transportation network, which can be transported quickly in the entire organism.” “The previous encounters imprinted in the network architecture have therefore become The decision to determine the future direction of the migration.”
Design based on general principles
“Given the simplicity of this network of activities, Physarum’s ability to form memories is fascinating. It is worth noting that organisms rely on such a simple mechanism to control it in such a delicate way.”
“These results provide an important puzzle for understanding the behavior of this ancient creature, and at the same time point out the general principles of behavior. We envision our findings in the design of smart materials and the construction of soft robots that can navigate in complex environments. Potential applications.” Karen Alim concluded.
Reference: Mirna Kramar and Karen Alim’s article “Encoding Memory in the Pipe Diameter Hierarchy of Live Streaming Network” on February 23, 2021, Proceedings of the National Academy of Sciences.
DOI: 10.1073 / pnas.2007815118