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Growth of Physarum flavicomum and Physarum rigidum in chemically defined minimal media
Abstract:
Physarum flavicomum, P. polycephalum, and P. rigidum grew at pH 4.2 in a medium composed of mineral salts, glucose, biotin, thiamine, hematin, and four amino acids. Important differences in pH tolerance were noted among the species. The minimal medium of P. flavicomum and P. polycephalum contained the amino acids methionine, glycine, and arginine, but valine was also required by P. rigidum. Starting with an inoculum of about 0.3 mg of protein per 25 ml of minimal medium, P. flavicomum and P. polycephalum grew to 23 mg and P. rigidum to 12 mg of protein per 25 ml in 3, 2, and 4 weeks, respectively. P. flavicomum and P. polycephalum grew with valine or leucine replacing arginine in the minimal medium but the growth yields and growth rates were decreased. All three species utilized homocysteine thiolactone in the minimal media in place of methionine. Serine adequately replaced glycine for P. rigidum but was inhibitory in the minimal medium of P. flavicomum or P. polycephalum unless homocysteine thiolactone also replaced methionine. Growth rates of all three organisms were increased in the presence of seven amino acids (original four plus leucine, lysine, and isoleucine).
Insights
Three Physarum species demonstrated distinct pH tolerances and amino acid requirements for growth. Optimizing media with specific amino acids like methionine and arginine enhanced growth rates and yields in these slime molds.
Area of Science:
- Mycology
- Biochemistry
- Cell Biology
Background:
- Physarum species are model organisms for studying cellular behavior and growth.
- Understanding their nutritional requirements is crucial for laboratory cultivation and research.
Purpose of the Study:
- To investigate the pH tolerance and specific amino acid requirements for the growth of Physarum flavicomum, P. polycephalum, and P. rigidum.
- To determine the impact of substituting or supplementing amino acids on growth rates and yields.
Main Methods:
- Cultivating three Physarum species in a defined mineral salts medium supplemented with glucose, essential vitamins, and specific amino acids.
- Varying amino acid composition and pH to assess growth responses, measured by protein yield over time.
Main Results:
- All three species grew at pH 4.2, but exhibited differential pH tolerance.
- P. flavicomum and P. polycephalum required methionine, glycine, and arginine, while P. rigidum also needed valine.
- Growth yields were highest when supplemented with a broader range of seven amino acids; homocysteine thiolactone could replace methionine, and serine could substitute glycine for P. rigidum.
Conclusions:
- Physarum species display specific nutritional dependencies and varying pH tolerances.
- Media optimization with essential amino acids significantly impacts Physarum growth, offering avenues for improved experimental protocols.