To ensure the life of microbial cells, micro-organisms are using from the natural environment nourishing substrates or food.The food means any medium on which micro-organisms can take action and to ensure that energy and all components necessary to biosynthesis of cellular components.
To use this medium as a source of nutrition in the microbial cell, by genetic and catabolic pathway, it regulates cell metabolism that allows adaptation to environmental conditions. In this sense microbial cells can synthesize adaptive extracellular enzymes that produce hydrolysis of nutrients and transport of nutrients into the cell and their conversion.
Nutrition conditions for the process are:
- In nutrient medium, microbial cells must enjoy conditions compatible with life;
- environment must provide the following nutritional components: water, carbohydrate sources-major sources of energy supply , nitrogen sources, mineral sources, growth factors;
In the absence of water, cell will not be able to feed, water making soluble environmental compounds, providing transport and transformation within the cell.
- aggregate water-soluble nutrients must be in a similar concentration to that available in cytoplasm, in order to avoid hypertonia of nutritional environment. Therefore culture media for growing micro organisms have a concentration of 3 to 15% rendering soluble nutrients.
- environment must be characterized by a certain pH, a specific oxidation-reduction potential, favorable to growth and multiplication of cells;
- Lack of toxic substances from environment or not to be possible for the processing of nutrients from the environment to form toxic substances.