What is the composition of MacConkey agar?
What is the composition of MacConkey agar?
Key components of the MacConkey medium include crystal violet dye, bile salts, lactose, and neutral red (pH indicator). Crystal violet dye and bile salts halt the growth of gram-positive bacteria. This allows only gram-negative species to form colonies on MAC agar.
How is MacConkey agar prepared?
Preparation of MacConkey Agar
- Suspend 49.53 grams of dehydrated medium in 1000 ml of distilled water.
- Heat to boiling to dissolve the medium completely.
- Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
- Cool to 45°C -50°C.
- Mix well before pouring into sterile Petri plates.
What are the components in the MacConkey broth?
MacConkey Broth Medium is a selective medium for the gram-negative bacterium….PROCEDURE FOR THE PREPARATION OF MACCONKEY BROTH MEDIUM.
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What is the enzyme in MacConkey agar?
Using the enzymes beta-galactosidase and beta-galactoside permeases, the most frequently encountered species of Enterobacter strains activate the pH indicator (neutral red) included in MacConkey agar, giving a pink or red stain to the growing colonies.
What ingredients MacConkey agar supplies carbon and nitrogen?
MacConkey Agar Base has peptic digest of animal tissue and proteose peptone, which provide nitrogen, carbon and vitamin source for the growth of bacteria. This medium does not contain carbohydrates. However for studying fermentation reaction, carbohydrate of interest has to be added while preparing medium.
What ingredients MacConkey agar supplies carbon?
Which ingredients in MacConkey agar supplies carbon? Gelatin, casein (milk protein), animal tissue, lactose, and to some extent, bile salts are potential sources of carbon.
What type of bacteria grow on MacConkey agar?
This only allows gram-negative species, which have a relatively bile-resistant outer membrane, to form colonies on MacConkey agar. ◈ Differentiation : Gram-negative bacteria that grow on MacConkey plate are differentiated by their ability to ferment lactose.
What is the selective agent in MacConkey agar?
The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose.
Is Mac selective or differential?
MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms.
What is the carbon source in MacConkey agar?
Lactose is a carbon source for energy. Sodium chloride supplies essential electrolytes and maintains osmotic equilibrium. Crystal violet and bile salts are selective agents which inhibit most gram-positive organisms.
What is the purpose of bile salts in the MacConkey agar?
MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms. Lactose provides a source of fermentable carbohydrate, allowing for differentiation.
Why is MacConkey agar yellow?
These bacteria do not ferment lactose; hence neutral red does not change to pink. Some of these bacteria can change the pH to alkali due to protein deamination. Increasing the pH of the media may result in a change in the color of media to yellow as neutral red turns yellow at alkaline pH.
Why MacConkey agar is selective?
MacConkey Agar Is Selective for Non-fastidious Gram-negative Organisms. Therefore, MacConkey needed a way to limit this background of environmental flora and allow only his organisms of interest to grow. A medium that can perform this function is now known as a selective medium.
What is the pH of MacConkey agar?
about 7.1+/- 0.2
The pH of the MacConkey agar medium is about 7.1+/- 0.2.
What type of isolation medium is MacConkey agar?
MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacteria and differentiate them based on lactose fermentation.
Why is MacConkey agar used?
◈ MacConkey Agar is a selective and differential medium used for the isolation and differentiation of non-fastidious Gram-negative bacilli, in particular members of the Enterobacteriaceae family and the genus Pseudomonas. ◈ Selectivity : Crystal violet dye and bile salts stop the growth of gram-positive bacteria.