Define the Nutritional Needs of Microorganisms?
About 95% of dry cell weight of microorganisms is constituted by macro elements. These are carbon (C), nitrogen (N), oxygen (O), hydrogen (H), sulphur (S), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and iron (Fe). In addition to macro elements, all microorganisms also require several microelements or trace elements. These are Iron (Fe), Manganese (Mn), Zinc (Zn), Cobalt (Co), Molybdenum (Mo), Nickel (Ni) and Copper (Cu).
These are normally a part of enzyme cofactor and helps in catalysis of reactions and maintenance of protein structures, e.g. Mo++ is needed for nitrogen fixation, Co++ is a part of Vitamin B12 and so on. Generally, these are obtained as contaminants from glassware, water and other media components. Micronutrients are generally ubiquitous in nature and probably do not limit the growth. Besides, common macro and trace elements, some microorganisms may have special nutrient requirements like, diatoms require silicic acid, many bacteria require high concentration of sodium ions and so on.