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The Growth Of Micro-Organisms

Growth: This is the gradual increase in size of an organism.

Micro-organisms: These are small tiny organisms that cannot be seen with the aid of an eye but with the use of a Microscope.

Characteristics of Micro-organism

All micro-organisms are made up of cells.

Micro-organisms are made up of pre-existing cells.

An organism with a single cell is called unicellular organism while an organism with several distinct cell with specialized functions are called multicellular organism.

Among organisms all bacteria, protozoans are unicellular organism while fungi maybe unicellular or multicellular likewise algae.


Bacteria are much smaller than Eukaryotic cell: they are cell with definite and well specialized nucleus, some bacteria’s such as Mycoplasma are too small to be clearly seen with an ordinary microscope because of the enormously small size of the organism, due to this reason, Electron Microscope is used to show the details structure of those mentioned bacteria cells. Bacteria can be in three shapes which are

Rod Shape (bacilus)
Spherical (coccus)
Curved Shape

All these shapes has each advantages, Rod Shape, with a large surface area are able to take up nutrients from the environment, while Spherical (cocci) are less prone to drying outs. The spiral forms are usually motile their shape aid their movement through an aqueous solution


Many fungi are dimorphic, that is they exist in two distinct forms. The cell wall of fungi is made up of chitin, a strong flexible polysaccharides that is also found in the exoskeleton of insects. The algae display a wide variety of structure, habitat and lifecycle. Algae posses pigment chlorophyll, they derive energy from the sun by means of oxygenic photosynthesis.


They are called unicellular protist. Protozoa are free living and inhabit fresh water to marine environment. Protozoan grow in a wide variety of moist habitats, moisture is absolute necessary for existence of protozoa.


Virus cannot be observed using a light microscope; they have no internal cellular structure. They are ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein. In general, viruses are much smaller than bacteria. Most viruses that have been studied have a diameter between 20 and 300 nanometres.

To obtain energy and construct new cellular components, organisms must have a supply of raw materials or Nutrients. Nutrients are substances used in biosynthesis and energy production and therefore are required for microbial growth. 

This chapter describes the nutritional requirements of micro-organisms, how nutrients are required and the cultivation of micro- organisms. 

Environmental factors such as temperature, oxygen level and the osmotic concentration. Hydrogen, oxygen, carbon, nitrogen, sulphur, phosphorus, potassium, calcium, magnesium, and iron are called macro elements or micronutrients because they are required by micro-organism in relatively large amounts. 

For example, potassium (k) is required for activity by a number of enzymes, calcium also contribute to the heat resistance of bacteria endospores.

Nutritional Requirement For Micro-Organism 

The microelement or micronutrient (carbon, oxygen, hydrogen, nitrogen, sulphur, potassium, phosphorus, calcium, magnesium and iron.) are required by micro-organisms in large amounts.
The first six micronutrients (Carbon, Oxygen, Hydrogen, Nitrogen, Sulphur and Phosphorus) are components of carbohydrate, lipids, proteins and nucleic acids. 

The remaining four macronutrients exists in the cell as cat ions (these are elements that are negatively charged (-ve) and play a variety roles. For example, potassium (k-) is required for activity by a number of enzymes (enzymes are catalysis which speed up the rate of a chemical reaction). Magnesium serves as a cofactor for many enzymes while calcium contributes to the heat resistance of bacterial endospores. 

All organisms, including micro-organisms also required several micronutrients. The micronutrients are manganese, zinc, cobalt, molybdenum, nickel and copper are needed by most cells.

The Requirements for Carbon, Hydrogen and Oxygen are:

The requirements of these three elements are satisfied together. Carbon is needed for the skeleton or backbone of all organic molecules, and molecules servingm as carbon sources normally also contribute both oxygen and hydrogen atoms, they also serves as energy sources. The more reduced the organic molecules are, the higher the energy content (e.g. lipids have a higher energy content than carbohydrates).

The Requirement for Nitrogen, Phosphorus, and Sulphur are:

Micro- organisms must be able to integrate large quantities of nitrogen, phosphorus, and sulphur in order to make them grow. Nitrogen is needed for the synthesis of amino acids, purines, pyrimidines, carbohydrates and lipids. Sulphur is needed for the synthesis of substances like carbohydrates, thiamine and also amino acids

Growth factors

Micro-organisms often grow and reproduce when minerals and sources of energy, carbon, nitrogen, phosphorus, and sulphur are supplied.

There are three major classes of growth
1) Amino acids,
2) Purines and Pyrimidines
3) Vitamins

Amino acids are needed for protein synthesis, purines, and Pyramidines for nucleic acid and synthesis. Vitamins are small organic molecules that usually make up all or part of enzyme cofactors, and only very small amounts sustain growth. These microelements and macroelement are so important to the effective growth of all micro-organisms. The adequate supply of these Nutrients is so essential

Submitted by Annix

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