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The function of slime from Physarum flavicomum in the control of cell division
Abstract:
A haploid cell of the myxomycete Physarum flavicomum undergoes cytokinesis, producing a large population of cells. However, after syngamy, cytokinesis no longer occurs but karyokinesis does and subsequent growth results in the formation of a diploid syncytial plasmodium. Slime, which is produced by the plasmodium but not the haploid cells, was aseptically isolated and purified, and tested for its effect as a cytokinetic regulator. Slime (a viscous, high molecular weight, acidic glycoprotein) affected cytokinesis of the haploid myxamoebae growing in pure culture in soluble media, and the effect was concentration dependent. In simple media, a slime concentration of about 6 10(-5) mug protein per cell suppressed cytokinesis about 50%, unequally inhibited the synthesis of protein, RNA, and DNA, but stimulated respiration. The biological activity of slime was not species specific and it also affected the bacterium Bacillus subtilis by inhibiting cytokinesis, stimulating oxygen uptake, and producing an aberrant cell morphology. Slime was inactivated by heat, fragmentation, and incubation with dithiothreitol, mercaptoethanol, and the proteolytic enzyme papain (EC 3.4.22.2). The inhibitory effect of slime on cell division of haploid cells could not be achieved using mucin or various polyanions. The possible role of slime in the production of the diploid syncytium is discussed.
Insights
A unique slime produced by Physarum flavicomum plasmodia regulates cell division. This slime inhibits cytokinesis in haploid cells and bacteria, impacting growth and morphology.
Area of Science:
- Cell Biology
- Biochemistry
- Mycology
Background:
- Haploid cells of Physarum flavicomum undergo cytokinesis, forming a large population.
- After syngamy, cytokinesis ceases, while karyokinesis continues, leading to a diploid syncytial plasmodium.
Purpose of the Study:
- To investigate the role of slime, produced by the diploid plasmodium, as a potential cytokinetic regulator.
- To characterize the effects of purified slime on haploid myxamoebae and other microorganisms.
Main Methods:
- Aseptic isolation and purification of slime from Physarum flavicomum plasmodium.
- Testing the effect of slime on haploid myxamoebae in pure culture, assessing concentration-dependent effects on cytokinesis, macromolecule synthesis, and respiration.
- Evaluating the species specificity of slime's biological activity using Bacillus subtilis.
- Determining slime inactivation methods (heat, fragmentation, enzymatic digestion).
Main Results:
- Purified slime acts as a concentration-dependent inhibitor of haploid myxamoebae cytokinesis.
- Slime unequally inhibited protein, RNA, and DNA synthesis while stimulating respiration in haploid cells.
- The slime's activity was not species-specific, affecting Bacillus subtilis by inhibiting cytokinesis, stimulating oxygen uptake, and causing aberrant morphology.
- Slime was inactivated by heat, fragmentation, and specific chemical treatments, including papain digestion.
Conclusions:
- The slime produced by Physarum flavicomum plasmodium functions as a potent cytokinetic regulator.
- Slime's ability to inhibit cell division and alter cellular processes suggests a role in the transition from haploid cells to a diploid syncytium.
- The findings provide insights into the biochemical mechanisms governing cell cycle regulation in myxomycetes.