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Biochemical Test

Biochemical tests are the tests that are performed on different bacteria for their identification on the basis of their biochemical activities towards different biochemical compounds.

  • Biochemical tests are one of the traditional methods for the identification of microorganisms, usually performed with phenotypic identification.
  • For many years these methods were employed extensively, and they continue to be used nowadays, especially in some laboratory routines where a particular type of microorganism has to be identified rapidly.
  • The ability of microorganisms to utilize certain biomolecules, resulting in useful organic compounds for themselves forms the basis of various biochemical tests.
  • Biochemical tests are of different types, where the identification or distinction between different microorganisms is made on various bases.
  • One of the traditional methods commonly used is a simple visual detection of the growth of the organism in the presence of essential nutrients by increased turbidity in the liquid medium.
  • In other tests, however, the results are based on the change in color of the medium as a result of the change in the pH of the medium.
  • Microorganisms can be classified into different groups on the basis of their reaction to such tests. Some tests even allow the distinction of microorganisms to the species level.
  • Biochemical tests are thus, essential as they are inexpensive and relatively simple to perform.
  • The physiology of bacteria and other microorganisms differs from one another, which allows for the differentiation of such microorganisms.
  • Biochemical tests, however, have some disadvantages. Despite being inexpensive and allowing both quantitative and qualitative information about the diversity of microorganisms present in a sample, these methods are laborious and time-consuming, and results are only observed after several days.
  • In some cases, false positives are obtained, especially when considering similar microbial species.

LAP Test- Principle, Procedure, Results, Uses

April 16, 2023 by Prashant Dahal
LAP Test

LAP test is used for the differentiation and identification of catalase-negative Gram-positive cocci bacteria. Specifically, it is used to distinguish Streptococcus, Enterococcus, Pediococcus, and Lactococcus species from Aerococcus and Leuconostoc … Read more

Lipid Hydrolysis Test (Lipase Test)- Principle, Procedure, Results

April 14, 2023 by Prashant Dahal
Lipid Hydrolysis Test

Lipid Hydrolysis Test (Lipase Test) is the biochemical test used to detect the ability of bacteria to produce exoenzyme lipase and hydrolyze lipids. Lipids are important components of the biological … Read more

Lecithinase Test (Nagler’s Reaction)- Principle, Procedure, Results

April 13, 2023 by Prashant Dahal
Lecithinase Test (Nagler's Reaction)

Lecithinase Test (Nagler’s Reaction) is a biochemical test for assessing bacteria’s ability to produce a toxic, phospholipase enzyme called ‘lecithinase’. Lecithinase (Phospholipase C) is a lipolytic enzyme, produced by some … Read more

Casein Hydrolysis Test- Principle, Procedure, Results

April 13, 2023 by Prashant Dahal
Result of Casein Hydrolysis Test

Casein Hydrolysis Test is the biochemical test used to determine the ability of bacteria to synthesize caseinase enzyme. Casein is the major protein (phosphoprotein) with a molecular formula of C81H125N22O39P, … Read more

KOH Test- Principle, Media, Procedure, Results, Uses

April 19, 2023April 12, 2023 by Prashant Dahal
Potassium hydroxide (KOH) test

KOH test, also known as KOH mount or KOH preparation, is a rapid test used to visualize the fungal structures in clinical samples using potassium hydroxide (KOH) as a clearing … Read more

Hydrogen Sulfide (H2S) Test: Principle, Procedure, Results

April 12, 2023 by Prashant Dahal
Hydrogen Sulfide (H2S) Test

Hydrogen Sulfide (H2S) Test is the biochemical test used to detect the ability of bacteria to produce H2S gas. Several bacteria and archaea can metabolically reduce sulfur-containing compounds to hydrogen … Read more

KIA Test- Principle, Media, Procedure, Results, Uses

April 11, 2023 by Prashant Dahal
Kligler’s Iron Agar (KIA) Test

Different bacteria have different enzyme systems and different biochemical activities to derive metabolic energy. Based on the enzyme system and biochemical characteristics, the end product of metabolism of the same … Read more

Pyruvate Broth Test- Principle, Procedure, Results, Uses

April 5, 2023 by Prashant Dahal
Pyruvate Broth Test

Pyruvate Broth Test is the biochemical test used to assess the ability of bacteria to utilize pyruvate and produce metabolic acid. Two pyruvates are produced as end products during glycolysis (aerobic … Read more

Salt Tolerance Test- Principle, Procedure, Results, Uses

April 4, 2023 by Prashant Dahal
Salt Tolerance Test

Salt Tolerance Test is the biochemical test used to determine the ability of bacteria to tolerate a high salt concentration (of 6.5%). Different genera of bacteria have different requirements for … Read more

PYR Test: Principle, Media, Procedure, Results, Uses

April 4, 2023 by Prashant Dahal
PYR Test

PYR test (L-Pyrrolidonyl-β-naphthylamide test) is a biochemical test used to detect the ability of bacteria to produce pyrrolidonyl aminopeptidase enzyme using L-Pyrrolidonyl-β-naphthylamide (PYR) as substrate. It was first reported in … Read more

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