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Introduction
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 simultaneously by organic
molecules in heterotrophs.
Organism and
source utilized
Carbon
Sources
Autotrophs
Energy Sources
Heterotrophs
Phototrophs
Chemotrophs
Lithotrophs
Organotrophs
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.
Growth factors:
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.
Nutrient uptake by cell:
For the cell growth and viability, cell must uptake the nutrients, it is important that the necessary
substances were up taken and not others. Specific mechanism is required to uptake the necessary
substance and not the unnecessary or toxic. As microorganisms often live in nutrient-poor
surrounding environments, they must be able to transport nutrients against a concentration
gradient. Bacterial plasma membrane is selectively permits the molecules to allow entry into the cell
which prevents unnecessary entry of toxic substance. Varieties of nutrients are available in
surrounding environment which allows microorganisms to use different transport mechanisms. The
most important mechanisms of these are facilitated diffusion, active transport, and group
translocation.
Culture media:
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.