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Potassium loss during galvanotaxis of slime mold
Abstract:
The posterior reticulated regions of the plasmodia of the slime mold, Physarum polycephalum, whose migration has been oriented by direct current (3.0 to 5.0 microa/mm(2) in the agar substrate), contain 30 per cent less potassium than the advancing non-reticulated region. The anterior regions have the same potassium concentration as that of the controls, approximately 32 meq/kg wet weight. Differences in potassium concentration between anterior and posterior regions of control plasmodia, not oriented by electric current, are less than 5 per cent. Sodium, in contrast to potassium, is generally less concentrated in the anterior than in the posterior regions of electrically oriented plasmodia, but sodium concentrations are extremely variable. No significant difference in protein concentration was found between oriented and control plasmodia. Thirty-five per cent of the total potassium, but none of the sodium, is found in acidified ethanol precipitates from plasmodial homogenates. Potassium, but not sodium, appears to be closely associated with processes which differentiate anterior from posterior in an oriented plasmodium.
Insights
Slime mold migration under electric current shows potassium redistribution. Posterior regions of Physarum polycephalum plasmodia contain less potassium, suggesting its role in directed movement.
Area of Science:
- Cellular Biology
- Biophysics
Background:
- The slime mold Physarum polycephalum exhibits directed migration in response to external stimuli.
- Electric fields are known to influence cellular behavior and migration patterns.
Purpose of the Study:
- To investigate the ion concentration changes, specifically potassium and sodium, in Physarum polycephalum plasmodia during electrically oriented migration.
- To determine the association of these ions with the differentiation of anterior and posterior regions in oriented plasmodia.
Main Methods:
- Physarum polycephalum plasmodia were subjected to direct current (3.0-5.0 microA/mm^2) in an agar substrate.
- Potassium and sodium concentrations were measured in anterior, posterior, and control regions of the plasmodia.
- Protein concentration and potassium association with cellular components were analyzed.
Main Results:
- Electrically oriented plasmodia showed a 30% lower potassium concentration in posterior reticulated regions compared to the advancing anterior region.
- Anterior regions maintained potassium concentrations similar to controls (approx. 32 meq/kg wet weight).
- Potassium, but not sodium, was found to be closely associated with processes differentiating anterior from posterior regions in oriented plasmodia.
Conclusions:
- Potassium redistribution is a key factor in the electrically oriented migration of Physarum polycephalum.
- The observed ion concentration differences highlight the role of potassium in cellular differentiation and directed movement within the plasmodium.
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