How a Single Cell Slime Mold Makes Smart Decisions

Physarum polycephalum

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The slime mold Physarum polycephalum includes a single biological cell. Microinjection permits to mark the circulation in Physarum in color. Credit: Bjoern Kscheschinski / MPIDS

How a single cell slime mold makes wise choices without a main nerve system.

Having a memory of previous occasions allows us to make smarter choices about the future. Researchers at the Max-Planck Institute for Dynamics and Self-Organization (MPI-DS) and the Technical University of Munich (TUM) have actually now determined how the slime mold Physarum polycephalum conserves memories – although it has no nerve system.

The capability to shop and recuperate details offers an organism a clear benefit when looking for food or preventing damaging environments. Traditionally it has actually been credited to organisms that have a nerve system.

A brand-new research study authored by Mirna Kramar (MPI-DS) and Prof. Karen Alim (TUM and MPI-DS) challenges this view by revealing the unexpected capabilities of an extremely vibrant, single-celled organism to shop and recover details about its environment.

Window to the past

The slime mold Physarum polycephalum has actually been perplexing scientists for lots of years. Existing at the crossroads in between the kingdoms of animals, plants and fungis, this distinct organism offers insight into the early evolutionary history of eukaryotes – to which likewise people belong.

Karen Alim

Prof. Karen Alim, Technical University of Munich, and Mirna Kramar, Max-Planck Institute for Dynamics and Self-Organization, found how the slime mold Physarum polycephalum weaves its memories of food encounters straight into the architecture of the network-like body and utilizes the saved details when making future choices. Credit: Bilderfest / TUM

Its body is a huge single cell comprised of interconnected tubes that form detailed networks. This single amoeba-like cell might extend numerous centimeters and even meters, including as the biggest cell in the world in the Guinness Book of World Records.

The network architecture as a memory

“It is very exciting when a project develops from a simple experimental observation,” states Karen Alim, head of the Biological Physics and Morphogenesis group at the MPI-DS in Göttingen and teacher for the Theory of Biological Networks at the Technical University of Munich.

When the scientists followed the migration and feeding procedure of the organism and observed an unique imprint of a food source on the pattern of thicker and thinner tubes of the network long after feeding.

Physarum polycephalum in Petri Dish

The slime mold Physarum polycephalum includes a single biological cell. Because of his innovative capability to adjust his tubular network to an altering environment, he has actually been called “intelligent”. Researchers at TUM and MPI-DS have actually now discovered how it shops details – even without having a nerve system or a brain. Credit: Nico Schramma / MPI-DS

“Given P. polycephalum’s highly dynamic network reorganization, the persistence of this imprint sparked the idea that the network architecture itself could serve as memory of the past,” states Karen Alim. However, they initially required to describe the system behind the imprint development.

Decisions are assisted by memories

For this function the scientists integrated tiny observations of the adaption of the tubular network with theoretical modeling. An encounter with food activates the release of a chemical that takes a trip from the area where food was discovered throughout the organism and softens televisions in the network, making the entire organism reorient its migration towards the food.

“The gradual softening is where the existing imprints of previous food sources come into play and where information is stored and retrieved,” states very first author Mirna Kramar. “Past feeding events are embedded in the hierarchy of tube diameters, specifically in the arrangement of thick and thin tubes in the network.”

“For the softening chemical that is now transported, the thick tubes in the network act as highways in traffic networks, enabling quick transport across the whole organism,” includes Mirna Kramar. “Previous encounters imprinted in the network architecture thus weigh into the decision about the future direction of migration.”

Design based upon universal concepts

“Given the simplicity of this living network, the ability of Physarum to form memories is intriguing. It is remarkable that the organism relies on such a simple mechanism and yet controls it in such a fine-tuned manner,” states Karen Alim.

“These results present an important piece of the puzzle in understanding the behavior of this ancient organism and at the same time points to universal principles underlying behavior. We envision potential applications of our findings in designing smart materials and building soft robots that navigate through complex environments,” concludes Karen Alim.

Reference: “Encoding memory in tube diameter hierarchy of living flow network” by Mirna Kramar and Karen Alim, 23 February 2021, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2007815118

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