The coagulase test is an analytical method that demarcates the staphylococci species into coagulase-positive and coagulase-negative species. Coagulase is an enzyme, which can either bound to the cell surface of bacteria as “Bound coagulase” or reside within the extracellular space as “Free coagulase”. Staphylococcus aureus, S. intermedius, S. hyicus are coagulase-positive organisms. Staphylococcus epidermis, S. saprophyticus, …
Oxidase test checks the production of cytochrome-c oxidases, whose presence in the test organism becomes evident by the formation of the blue-purple coloured complex (indophenols). It uses TMPD (tetramethyl phenylenediamine dihydrochloride) reagent. In an oxidized state, TMPD develops a blue-purple coloured complex while remains colourless in a reduced state. Therefore, we can say that the …
Catalase test is one of the biochemical analysis that generally comes into use in identifying the organisms (whether they are catalase producers or not). It is primarily used to distinguish between the two classes of gram-positive bacteria, namely Staphylococcus and Streptococcus species. Streptococcus bacteria are mostly facultative anaerobes (may produce catalase), while few are obligate …
Voges Proskauer test depends upon the formation of a neutral end product “Acetoin” in the MRVP media, which directly relies on the breakdown of glucose into an intermediate product, pyruvic acid. The pyruvic acid enters the butylene glycol pathway and produces an end product named acetyl methyl carbinol or acetoin. It is named after the …
Methyl red test differentiates whether a test organism can undergo mixed acid fermentation or not by allocating adequate glucose. Organisms that can ferment glucose will give a positive MR test by producing a large amount of acid, while some organisms give a negative MR test. MR-test also helps to identifying and categorizing the different genera of …
The citrate utilization test distinguishes different genera of enteric group based on the property of citrate utilization through an enzyme catalyst (Citrase). Test organisms form many by-products by the time they utilize citrate incorporated in the test media. By the complete hydrolysis of citrate, an alkaline product (sodium carbonate) forms that cause alkalinity in the …
Indole test is a biochemical test determining and classifying the bacteria based on their tendency to decompose amino acid (Tryptophan) into a heterocyclic organic compound (Indole). It is a part of a biochemical method popularly known as the IMViC test, in which ‘I’ stands for the indole test. Indole is one of the end products …
Bacterial conjugation is a gene transfer mechanism introduced by the scientists named Lederberg and Tatum in 1946. The conjugation method was first studied in Escherichia coli. The formation of a conjugation tube is the characteristic feature of a conjugation mechanism. Besides transduction and transformation mechanisms, some bacteria passes the genetic information from a donor to …
SOS repair or “bypass” or “Emergency” repair is one of the DNA repair mechanisms introduced in 1975 by a scientist named Miroslav Radman. SOS repair primarily recovers the DNA damage caused due to environmental stresses. It serves as a regulatory system, which comprises many complex inducer proteins that repair the damaged DNA. SOS system also …
Oxidation pond or lagoon or water stabilization pond is a secondary wastewater treatment that treats waste or sewage coming from industries, residential areas, etc. It uses microorganisms like bacteria, algae and light energy (sunlight) to stabilize the wastewater. The oxidation pond is constructed 1-1.5 m deep inside the soil and provided with inlet and outlet systems. …