|
Principle
- Yeast mannitol agar is used for the isolation of nitrogen-fixing Rhizobium from rood nodules and rhizospheric soil samples. It is composed of yeast extract, mannitol, dipotassium phosphate, magnesium sulfate, sodium chloride, congo red, and agar.
- Yeast extract serves as a good source of readily available amino acids, vitamin B complex, and accessory growth factors for Rhizobia. It also aids in the oxidation-reduction potential of the medium in the range favorable for Rhizobia and serves as a hydrogen donor in the respiratory process.
- Mannitol is the carbon source. Dipotassium phosphate resists the change in pH of the medium. Magnesium provides cations essential for the growth of Rhizobia. Congo red inhibits penicillin-susceptible strains.
- Colonies of Rhizobia stand out as white, translucent, glistening, and elevated, with entire margins
|
