The bile solubility test is a biochemical test that distinguishes bile soluble and bile resistant α-haemolytic Streptococci. Streptococcus pneumoniae is the only strain that emulsifies by reacting with the bile solubility reagent, whereas the other α-haemolytic Streptococci do not undergo such reaction. The reason for the dissolution of the Streptococcus pneumoniae is due to the …
Urease test is an analytical method practised to identify the urease positive and negative organisms based on the production of cytosolic urease enzyme. It distinguishes the Proteus species from the non-lactose fermenting members belonging to the Enterobacteriaceae family. Urease test makes the use of urea base. Conventionally, Stuart formulated urea broth was used to identify …
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 …