METHYL RED TEST

 

METHYL RED TEST

Aim

To differentiate the organism for the production of large amount of acid during fermentation of glucose.

Principle

The methyl red (MR) test identifies bacteria capable of producing stable acidic end products from glucose fermentation. MR test along with the VP test is performed simultaneously because they are physiologically related and are performed in MRVP broth. Bacteria which metabolizes pyruvic acid by the mixed acid pathway, produces more acid end products, such as lactic acid and acetic acid, and maintain an acidic environment. The methyl red detects mixed acid fermentation that lowers the pH of the broth. The MR indicator is added after incubation which is red at pH 4.4 and yellow at pH 6.2. If the organism produces a large number of organic acids that include formic acid, acetic acid, lactic acid, and succinic acid from glucose fermentation, the broth medium will remain red after the addition of methyl red, a pH indicator. MR-negative organisms metabolize the products by decarboxylation to produce neutral acetyl methylcarbinol (acetoin), which results in decreased acidity in the medium and raises the pH towards neutrality (pH 6.0 or above).  For those organisms which do not produce the acid end products, the broth medium will change to yellow coloration indicating a negative test.


Materials required

·       24-48 hour old bacterial culture

·       MR VP tubes (5 ml in each tube)

·       MR reagent

·       Dropper

·       Inoculating loop

·       Bunsen burner


Pr   Procedure

Ø  5 ml of MR -VP broth was inoculated with test organism.

Ø  The tubes were incubated at 37oC for 24-48 hours.

Ø  0.5 ml(5 drops) of MR reagent added to 24-48 hour old broth culture.


Result

The culture which shows positive result yields red colour, If the broth remains orange, the test must be repeated. The yellow colour indicates negative result.

Examples

Positive: E coli, Staphylococcus sp, Proteus sp

Negative: Peudomonas sp, Bacillus sp

Comments

Post a Comment

Popular posts from this blog

Biological databases

 Biological databases A database is a computerized archive used to store and organize data in such a way that information can be retrieved easily via a variety of search criteria. Databases are composed of computer hardware and software for data management. The chief objective of the development of a database is to organize data in a set of structured records to enable easy retrieval of information. Each record, also called an entry, should contain a number of fields that hold the actual data items, for example, fields for names, phone numbers, addresses, dates. To retrieve a particular record from the database, a user can specify a particular piece of information, called value , to be found in a particular field and expect the computer to retrieve the whole data record. This process is called making a query. Biological databases are  libraries of biological sciences, collected from scientific experiments, published literature, high-throughput experiment technology, and compu...
Read more

Cell membrane /Plasma membrane

Image
    Plasma membrane or cell membrane Plasma membrane or cell membrane is a dynamic , fluid structure and forms external boundary of the cell. It acts as a selective permeable membrane and regulates molecular traffic across the boundary. Plasma membrane behaves as a capacitor. In absence of integral membrane proteins, plasma membrane have similar electrical properties. The non conductive lipid bilayer of the membrane separates the conductive extracellular and intracellular electrolyte solutions. This results in the separation of charge across the lipid bilayer and this charge separation   brings about an electrical potential difference across the bilayer which is referred to as membrane potential. Different models are: Overton model The Overton model, (1899)  proposed by Charles Overton, suggests that the plasma membrane is primarily composed of lipids, and its permeability is largely determined by the lipid solubility of substances. This model is based...
Read more

RASMOL/RASWIN

  RASMOL/RASWIN Show information and Background Aim To display information about the protein selected and to change the background color. Description RasMOL is a computer program written for molecular graphics visualization intended and used mainly to depict and explore biological macromolecule structure, such as those found in the protein data bank . It was originally developed by Ronger Dayle in the early 1990s.RasMOL includes a scripting language, to perform many functions such as selecting certain protein chains, changing colours etc. Jmol Sirus software have incorporated this language into their commands.   Procedure STEP 1: Open RasMol STEP 2: Open a new PDB file of protein Command RasMol.>Show information RasMol.>background white Output(take print) Result Information about the selected protein was displayed and background color was changed to white.               Show Sequenc...
Read more