On mass transport in Physarum polycephalum

by Felix Kaspar Bäuerle
Doctoral thesis
Date of Examination:2019-06-07
Date of issue:2019-12-20
Advisor:Dr. Karen Alim
Referee:Dr. Karen Alim
Referee:Prof. Dr. Eberhard Bodenschatz
Persistent Address: http://dx.doi.org/10.53846/goediss-7786

 

 

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Abstract

English

The network-forming slime mold Physarum polycephalum has proven to be the epitome of self-organization. As a single cell it adapts seemingly intelligent to stimuli, integrating various inputs to create a coordinated response over an extended body plan in space and time. Most feats performed by Physarum polycephalum are linked to its morphology which is constantly reforming by transporting mass from pruning parts to growing ones. Cytoplasmic ows, the means for mass transport, are directly linked to periodic contraction patterns. Here I investigate induced mass transport in slime molds via two complementary methods: Firstly, I follow the reorganization of Physarum polycephalum networks after severe wounding and secondly I present that modulating the phase di erence between harmonics increases the pumping e ciency in the slime mold when subjected to blue light. Spatial mapping of the contraction changes in response to wounding reveal a multi-step pattern. Phases of increased activity alternate with cessation of contractions and stalling of ows, giving rise to coordinated transport and growth at the severing site. Overall, severing surprisingly acts like an attractive stimulus enabling healing of severed tubes. Furthermore I show that a modulation of the phase di erence between harmonics, given cost-free constraints, directly in uences the pumping e ciency by adjusting the pumps maximal occlusion. I nd that the slime mold adapts its waveform accordingly when evacuating an area. It can thereby react to its environment in a self-organized fashion without changing its energy demand. Wounding is a severe impairment of function, especially for an exposed organism like the network-forming true slime mould Physarum polycephalum and wavelike patterns driving transport are ubiquitous in living systems. The presented results may open up new venues to investigate the biochemical wiring underlying P. polycephalum’s complex behaviours, provide a novel metric for wavelike patterns in general and demonstrate the crucial role of nonlinearities in living systems.
Keywords: Biophysics; Biofluidics; Fluid dynamics; Wave patterns; Peristalsis; Physarum polycephalum
 
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