Methyl red test(mr test)

Methyl red test(mr test)

• 1.
  METHYL REDTEST(MRTEST) BY-MOHIT HINSU
• 2.
  INRODUCTION: ■ Methyl redtest – Biochemical test ■ Use-To determine fermentation capacity of given bacterial culture. ■ This test one part of IMViC test. ■ AIM:To carry out methyl red test to determine fermentation capacity of given bacterial culture.
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  PRINCIPLE: ■ Some bacteria[Enterobacteriaceaefamily] have the ability to utilize glucose and convert it to a stable acid like lactic acid, acetic acid or formic acid as the end product. ■ These bacteria initially metabolise glucose to pyruvic acid, which is further metabolized through the ‘mixed acid pathway to produce the stable acid.The type of acid produced differs from species to species and depends on the specific enzymatic pathways present in the bacteria.The acid so produced decreases the pH to 4.5 or below, which is indicated by a change in the colour of methyl red from yellow to red. ■ In the methyl red test (MR test), the test bacteria is grown in a broth medium containing glucose. If the bacteria has the ability to utilise glucose with production of a stable acid, the colour of the methyl red changes from yellow to red, when added into the broth culture.
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  ■ REQUIREMENT: ■ Glucosephosphate broth ■ Methyl red indicator ■ Test culture ■ MEDIA COMPOSITION OF GLUCOSE PHOSPHATE BROTH: ■ Glucose 0.5 gms ■ K2HPO4 0.5 gms ■ Peptone 0.5 gms ■ Distil water 100 ml ■ pH 7
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  ■ PROCEDURE: ■ Glucosephosphate broth is prepared and distributed in test tubes these test tubes are further sterilized by autoclaving.[121C for 15 min, covered test tube properly ]. ■ The sterile test tubes are inoculated with test culture and incubated at 37C for 48 hours. ■ Add 5-6 drops of methyl red indicator per 5 ml broth. ■ Observe for the colour change in the broth medium.
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  ■ OBSERVATIONAND RESULT: Positive:Bright red color Weakly positive: Red-orange color Negative: Yellow color