MacConkey agar – Composition, Principle, Uses, and Preparation | Biology Ideas

What is MacConkey Broth?

MacConkey Broth is a modification of the medium developed by scientist MacConkey.

MacConkey Broth is used for the cultivation of gram-negative Bacteria.

MacConkey broth (MacConkey agar)

 

Storage of MacConkey’s Broth

MacConkey’s Broth medium should be kept upright at 2-30 °c.

Adequate storage definitely increases the life and quality of the product.

Freezing and overheating will cause the scale to deteriorate of the medium.

MacConkey’s Broth should not be used beyond the expiration date.

Expiration dates apply to tubes and packages that can be opened, adequately stored.

 

Composition of MacConkey Broth

  1. Peptone – 20 gm
  2. Sodium taurocholate – 5 gm
  3. Lactose – 10 gm
  4. Sodium chloride (NaCl) – 5 gm
  5. pH – 7.2
  6. Distilled water – 1 liter
  7. Neutral red (1% sol.) – 4 ml
IngredientsAmount
Peptone 20 gm
Sodium taurocholate 5 gm
Lactose10 gm
Sodium chloride (NaCl) 5 gm
Neutral red (1%)4 ml
Distilled Water1 Liter (As our need)

 

Preparation of MacConkey broth

  1. The dye should be added only after adjusting the pH.
  2. Distribute 10 ml in different test tubes.
  3. Put Durham’s tubes in an inverted position in these tubes.
  4. Sterilize by autoclaving at 121 °c for 15 minutes.

 

What is MacConkey agar?

MacConkey agar (MAC) is a solid differential media.

This agar is developed in the 20th century by Alfred Theodore MacConkey.

It is a solidifying agent which solidifies the liquid medium.

 

Composition of MacConkey agar

  1. Peptone – 20 gm
  2. Sodium taurocholate – 5 gm
  3. Lactose – 10 gm
  4. Sodium chloride (NaCl) – 5 gm
  5. Distilled water – 1 liter
  6. pH – 7.2
  7. Neutral red (1% sol.) – 4 ml
  8. Agar – 2-3%
IngredientsAmount
Peptone 20 gm
Sodium taurocholate 5 gm
Lactose10 gm
Sodium chloride (NaCl) 5 gm
Neutral red (1%)4 ml
Agar (2-3%) 13.5 gm
Distilled Water1 Liter (As our need)

 

Preparation of MacConkey agar

  1. Sterilize by autoclaving at 121 °c for 15 minutes.
  2. The method of plates preparation is the same as that of Nutrient agar. This medium is used for the cultivation of enteric bacteria.
  3. Sodium taurocholate ( bile salt) inhibits non-enteric bacteria. The lactose fermenters ( E.coli, Klebsiella spp.) utilize lactose in the medium and produce acid and gas.
  4. Acid production changes colour from neutral red to pink and gas production is detected in inverted Durham’s tubes in MacConkey’s broth tubes.
  5. In MacConkey’s agar plates color of colonies of lactose fermenting organisms are pink and are opaque as at acidic pH, neutral red precipitates in the colony.
  6. Lactose non-fermenters (Salmonella spp. and Vibrio spp.)show no pink coloration around the colony, in fact, the medium changes the colour to yellow and the colonies remain translucent.

 

Uses of MacConkey agar

  • MacConkey agar is used in selective and differential media for the isolation and differentiation of non-fastidious gram-negative rod-shaped bacteria, particularly members of the family Enterobacteriaceae and the genus Pseudomonas.
  • It is also used for the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria.
  • MacConkey agar is used for the isolation as well as differentiation of gram-negative bacteria.

 

Limitations of MacConkey Agar

  • Some strains may be encountered that grow poorly or fail to grow on this medium.
  • Some strains may swarm on MacConkey Agar medium.

 

Result and Observation of MacConkey Agar

Result and Observation of MacConkey Agar

“Lactose fermenting strains, grow red or pink and may be surrounded by a zone of acid precipitated bile. The red colour is due to the production of acid from lactose, absorption of neutral red, and a subsequent colour change of the dye when the pH of the medium falls below 6.8.”

“Lactose non-fermenting strains, such as Shigella and Salmonella are colourless and transparent and typically do not alter the appearance of the medium. Yersinia enterocolitica may appear as small, non-lactose fermenting colonies after incubation at room temperature.”

 

 

References

http://www.cabri.org/guidelines/micro-organisms/M203Ap1.html

https://microbiologyinfo.com/macconkey-agar-composition-principle-uses-preparation-and-colony-morphology

https://en.wikipedia.org/wiki/MacConkey_agar

https://microbeonline.com/macconkey-agar-mac-composition-preparation-uses-and-colony-characteristics

https://www.carlroth.com/com/en/media-for-salmonella-shigella/macconkey-agar/p/x922.1

 

You may also like to read following articles

Monochrome Staining – Principle, Procedure and Result | Biology Ideas

Acid fast staining of bacteria – Principle, Procedure, and Result

Negative Staining – Requirements, Principle and Procedure | Biology Ideas

Instruments used in Microbiology Laboratory – Principle and Uses | Biology Ideas

Algae – Definition, Classification and Examples | Biology Ideas

Preparation and Sterilization of culture media | Biology Ideas

Leave a Comment

Share via
Copy link
Powered by Social Snap