Related Experiment Videos
Studies on microplasmodia of Physarum polycephalum. I. Classification and locomotion behavior
Abstract:
Depending on the conditions of the axenic shuttle culture, microplasmodia of the acellular slime mold Physarum polycephalum can be subdivided into three classes regarding fine structural organization and protoplasmic streaming activity: (1) spherical and rod-shaped types, (b) ameboid types, and (c) symmetrical types. In ameboid microplasmodia, the motive force for the irregular protoplasmic streaming activity is generated by alternative contraction and relaxation of a membrane-associated layer, morphologically consisting exclusively of thin filaments (probably actin). The protoplasm flows along a hydraulic pressure gradient produced by the filament layer within limited regions of the cell periphery. In dumbbell-shaped microplasmodia the motive force for the regular protoplasmic shuttle streaming between the two spherical heads is generated both by volume changes of the peripheral cell region (caused by the contractile activity of the membrane-associated filament layer), and by volume changes of the internal cell membrane invagination system (caused by fibrils attached to the basal region of the invaginations). The development from the unordered protoplasmic streaming pattern and less complicated fine structural organization in ameboid microplasmodia to the highly organized protoplasmic shuttle streaming and the more complicated morphology in dumbbell-shaped microplasmodia can be explained by intermediate stages. Whereas the motive force for the transport of smaller amounts of protoplasm can be generated by the exclusive action of a cortical filament layer, the existence of a filament cortex, the display of cytoplasmic fibrils, and the development of plasma membrane invaginations appear to be a necessary precondition for the transport of large amounts of protoplasm.
Insights
Physarum polycephalum microplasmodia exhibit three types based on structure and streaming. Actin filaments drive protoplasmic movement, with complex structures facilitating larger transport in slime mold cells.
Area of Science:
- Cell Biology
- Biophysics
Background:
- The acellular slime mold Physarum polycephalum exhibits diverse microplasmodial forms.
- Understanding the mechanisms of protoplasmic streaming is crucial for cell motility research.
Purpose of the Study:
- To classify Physarum polycephalum microplasmodia based on structure and streaming.
- To elucidate the motive forces behind protoplasmic streaming in different microplasmodial types.
Main Methods:
- Axenic shuttle culture of Physarum polycephalum.
- Fine structural analysis of microplasmodia.
- Observation of protoplasmic streaming activity.
Main Results:
- Three classes of microplasmodia identified: spherical/rod-shaped, ameboid, and symmetrical.
- Amoeboid streaming is driven by actin filament contractions in the cell periphery.
- Dumbbell-shaped microplasmodia utilize both peripheral and internal membrane system changes for streaming.
Conclusions:
- Protoplasmic streaming complexity correlates with microplasmodial morphology.
- Actin filaments are essential for motive force generation.
- Advanced structures like filament cortex and membrane invaginations are necessary for large-scale protoplasm transport.