PHYSICAL AND IONIC REQUIREMENTS

K2HPO4 + HCI - KH2PO4 + KCI If, however, a strong base is added, the opposite conversion occurs  

In the preparation of synthetic media, sometimes precipitates form upon sterilization, particularly if the medium has a relatively high phosphate concentration. The precipitate results from the formation of insoluble complexes between phosphates and mainly calcium and iron cations. By sterilizing the calcium and iron salts separately and then adding them to the sterilized and cooled medium, the problem can be avoided. 

Alternatively, a chelating agent such as EDTA (ethylenediamine tetraacetic acid), may be added at a concentration of approximately 0.01%, to form a soluble complex with these metals. When two or more microorganisms are placed in a medium, their combined metabolic activities may differ, either quantitatively or qualitatively, from the sum of the activities of the individual members growing in isolation in the same medium. Such phenomena result from nutritional or metabolic interactions and are collectively termed synergistic effects.0 1 

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