Hofer’s Alkaline Medium is used for selective isolation of Agrobacterium species while inhibiting Rhizobium species from soil samples. It is a selective medium with high alkaline pH. Agrobacteria grow at higher pH while Rhizobia fail to grow at alkaline pH. The medium is supplemented with mannitol as the carbohydrate or carbon source.Yeast extract provides nitrogenous nutrients. Sodium chloride maintains osmotic balance of the medium. Dipotassium phosphate buffers the medium. Thymol blue is the pH indicator, which remains blue at high alkaline pH.
1.Balows A., Truper H. G., Dworkin M., Harder W., Scheifer K. H., (Eds.), The Prokayotes, 2nd Edition, Springer- Verlag,New York Inc. 2.Subba Rao N. S., 1977, Soil Microorganisms and Plant Growth, Oxfordand IBH Publishing Co., New Delhi.