Bacteria are the complex group of living things. Bacteria consist of only one cell.

There are various species of bacteria, having one of the following shapes:

  1. Rod
  2. Coccus
  3. Spiral

Some bacteria can live in temperatures above the boiling point and in cold below the freezing point. Bacteria may be helical or spiral in shape. Some bacterial cells exist as individuals while others live in cluster together to form pairs, chains, squares or other formations.

Microorganisms have a significant impact on human life by their beneficial and harmful activities. Since time immemorial, the pathogenic microbes have been a cause of concern for the society. Deadly infectious diseases like AIDS, Leprosy, Meningitis, etc. causes large scale morbidity and mortality. Besides, microorganisms also cause a number of plant diseases leading to massive economic setbacks. However, the useful activities of microbes far outnumber their harmful ones. Besides, with the latest advances in biological sciences and technology, it is now possible to manipulate microbes for the benefit of mankind.
Bacteria have been used for decades for generation of specific products with industrial and medical applications. Products like organic acids, solvents, enzymes, amino acids, etc. have immense economic value. They can be used as food supplements, additives and in pharmaceuticals. Besides, medical compounds like hormones, antibiotics, transformed steroids etc. will go a long way in alleviating human suffering. Bacteria and Viruses also have a significant role in environment management. They are important components of biogeochemical cycles with a major role in biodegradation.

Biochemical tests are the tests that are used for the identification or confirmation of different bacterial species or different micro organisms based on the biochemical activities that the microorganisms are performing.

In order to classify different bacteria as unique or different from each other it is needed to identify them as unique and to do so their structural and chemical differences are identified. Structural differences are identifies on the basis of their morphology and the chemical differences are identified on the basis of their biochemical properties which are classified on the basis of the results of different biochemical tests performed on the bacteria.

The structural differences such as shape, size and morphology of bacteria do not help much if we want to identify the different species of the bacteria, because there are various species of bacteria that have similar shape, size and arrangement. Hence, the identification of bacteria should majorly be based on the differences in the bacterial biochemical.

Some bacterial species perform a metabolic process which is known as fermentation, where they utilize sugars and produce ATP or also known as the energy source of the bacteria. The utilization of the sugar depends upon the specific enzymes that the bacteria shall possess. Bacteria use the nutrients that are present in their environment (for example, the media in which they are inoculated) to produce ATP (energy source) for their biological processes such as growth (i.e. cell division) and reproduction. Many bacteria possess the enzyme system required for the oxidation and utilization of the simple sugar, glucose. Some bacteria have the ability to break down complex carbohydrates like lactose, sucrose or even polysaccharides, into simpler sugars that they can then utilise to produce energy required by other metabolic processes.

Such bacteria shall have the required enzyme that is able to cleave the bonds between the sugar units so the resulting simple carbohydrate can be transported into the cell.

Glucose is the sugar that we get from almost every food that we eat and the body uses it to produce energy for our metabolism. It is the simplest form of carbohydrate.

Sucrose is the common sugar that we use in day to day life. It is comprised of glucose and fructose. The enzyme sucrase breaks down the sucrose (also known table sugar) into its constituent units i.e., glucose and fructose.

Lactose is a disaccharide consisting of the glucose and galactose bonded by glycosidic bond. The bacteria which produce the enzyme lactase has the ability to break this bond and thus release free glucose that can easily be utilized by the bacteria, hence, lactase breaks lactose (or milk sugar) into glucose and galactose.

Mannitol is a sugar alcohol most commonly used as a medication. It is given to diabetic patients as it is poorly absorbed in intestine.
This ability of the bacteria to produce such enzymes enables them to use various carbohydrates which in turn help in the identification of unknown bacteria.