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Elements (Macro and Micro) are the essential components of every living organism. As many biochemical reactions are processed simultaneously in cell viz. protein synthesis, RNA synthesis, DNA synthesis, carbohydrate, protein, and lipid metabolism, energy production, detoxification of toxic materials, etc. To carry out these biochemical reactions, organisms must have a supply of raw materials or nutrients.
The elemental analysis of dry bacterial cells shows present of few major elements like carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, Calcium, Magnesium, Iron. These elements are required relatively in large amount and so called macroelements or macronutrients. Macroelements are components of proteins, lipids, carbohydrate, nucleic acid, as co-factor in protein synthesis, DNA synthesis, energy production, transcription, etc.
Apart from the macroelements, all organism requires several other nutrients in vary minute quantity. These are known as micronutrients or trace elements and are manganese, zinc, cobalt, molybdenum, nickel, and copper. Either they are part of enzymes and cofactors or they play an important role in catalysis and maintenance of protein structure.
Carbon Hydrogen, Oxygen and Electron
All reaction requires energy in the form of electron, either accept the electron or donate the same. In case of heterotrophs (organisms that use reduced, preformed organic molecules as their carbon source) electron source is organic molecules, whereas autotrophs use CO2 as a carbon source they get energy from light or reduced inorganic molecules (Figure 1). As discussed earlier there are only two energy source available to all organism, either light or oxidizing organic or inorganic molecules. The requirement of carbon, hydrogen and oxygen can be served by organic molecules in heterotrophs.
Figure 1: Classification of organism based on their source of carbon, energy and electron.
Nitrogen, Phosphorus and Sulphur:
Nitrogen, Phosphorus and Sulphur are equally important like carbon, hydrogen and oxygen for all the cells including synthesis of amino acids, purines, pyrimidines, some carbohydrates and lipids, enzyme cofactors, nucleic acids, phospholipids, nucleotides like ATP, several cofactors, some oacid proteins, and other cell components. Basic source of nitrogen is amino acid; others can use ammonia directly through the action of enzymes such as glutamate dehydrogenase or glutamine synthetase and glutamate synthase. Inorganic phosphate is the prime source of phosphorus, and almost all bacteria incorporate it directly. Assimilatory reduction of sulphate is the common source of sulphur.
Nature has gifted some of the organism with enzymes and biochemical pathways needed to synthesise all cell components using minerals sources of energy, carbon, nitrogen, phosphorus, and sulphur, on the other hand other microorganism lacks one or more of them to do the same. The remaining organisms have to obtain the ready or their precursors from the nature, these components which are not synthesized by cell but essential for cell is called growth factors. Growth factors can be divided into three major classes 1. Amino acids, 2. Purines and pyrimidines, and 3. Vitamins. Amino acids are the building blocks of proteins, purines and pyrimidines are the basic unites of DNA and RNA, vitamins are may be a part of enzyme co factors and are required in very small quantities. Understandings of growth factor requirement are important to design bioassay for the vitamins or amino acids, production of vitamins, etc.
Microorganism grows in laboratory when ideal conditions are provided like temperature at which they grow agitation if organism is aerobic, required nutrients in the form of media. Nutrients are the essential components of life and unavailability of any of the essential component inhibit the growth of organism. Culture media can be divided in to two broad classes generalized media and specialized media. Generalized media have all necessary components which facilitate growth of almost all microorganisms, where as in contrast to it specialized media facilitate only a particular organism or a class of organism.