Talk by Dr. Karen Alim

On Wednesday, December 06, 2017, Dr. Karen Alim (Max Planck Institute for Dynamics and Self-Organisation, Göttingen) will give a talk in the context of the colloquium series of the CBI in WT 2017/2018. The talk is entitled "How are slime moulds thinking? - Signal transduction by fluid flows" and will be held at the Center for Bioinformatics (CBI), building E2 1, lecture room 001, ground floor at 17:00 am.

Abstract:

The acellular slime mould Physarum polycephalum is renown for its ability to solve complex tasks like finding the shortest path through the maze and connecting food sources in what seems a robust and efficient transport network. The complex behaviors go hand in hand with fluid flows extending throughout the network-shaped body plan of the slime mould. Flows are very large as they are coordinated in a peristaltic wave driven by periodic contractions of all tubes making up the network. What drives communication across the tubular network? What drives the self-organization of the tubes to undergo rhythmic contractions and form such long-ranged peristaltic waves? Searching for the mechanism of signal propagation in slime molds we find that, flows are hijacked by signals to propagate throughout the network. Signals promote their own transport by invoking a propagating front of increased flow. These simple non-linear dynamics are sufficient to explain surprisingly complex dynamics of the organism like finding the shortest path through a maze. Importantly, we find that distant parts within the tubular network communicate by fluid flow. We investigate the mechanism behind the self-sustained contractile waves by studying the dynamics of simple loop-shaped tubes. In experiment, we observe both traveling waves and standing waves of contractions. We build a mechano-chemical model, where a chemical triggers tube contractions, but is at the same time transported by the fluid flows in the tube. Chemical concentration feeds back to the contractions and thereby we predict long-wavelength traveling waves in looped tubes. Taking also variations in tube radius along the loop into account we recover switching between traveling and standing waves in accordance with observations, substantiating our model of self-organization.