What Ingredient Makes EMB Agar Differential?

What does EMB contain that allows E coli to be red or purple?

The selective/ inhibitory agents of EMB are the dyes eosin Y and methylene blue.

Methylene blue inhibits the gram + bacteria (eosin to a lesser extent), while eosin changes color, to a dark purple, when the medium around the colony becomes acidic..

What does EMB stand for?

EMBAcronymDefinitionEMBEvery Man’s BattleEMBEndometrial BiopsyEMBEndomyocardial Biopsy (cardiology)EMBEmail Me Back39 more rows

What would growth on EMB and MacConkey Agars suggest?

By plating organisms in both EMB and MacConkey agars we would be able to detect gram-negative organisms, and more specifically E. coli from other enteric organisms.

How do you make EMB Agar?

Preparation Instructions Suspend 36 grams of EMB Agar in 1000 mls of distilled water. Heat to dissolve the medium completely. Dispense and sterilize by autoclaving at 15 lbs. pressure (121 °C) for 15 minutes.

What Agar does E coli grow on?

E coli is a gram-negative bacillus that grows well on commonly used media. It is lactose-fermenting and beta-hemolytic on blood agar.

How EMB media differentiate bacteria?

Eosin Methylene Blue (EMB) agar is a differential microbiological medium, which slightly inhibits the growth of Gram-positive bacteria and provides a color indicator distinguishing between organisms that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella).

Is E coli gram positive?

Escherichia coli (commonly abbreviated E. coli) is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans.

Why does EMB inhibit gram positive?

Eosin–Methylene Blue (EMB) Agar is a differential medium for the detection of Gram negative enteric bacteria. … The growth of Gram positive bacteria is generally inhibited on EMB agar because of the toxicity of methlyene blue dye.

What color is E coli on nutrient agar?

coli on Nutrient Agar (NA) 1. They appear large, circular, low convex, grayish, white, moist, smooth and opaque.

What morphology is E coli?

E. coli is gram-negative (-ve) rod-shaped bacteria. It is 1-3 x 0.4-0.7 µm in size and 0.6 to 0.7 µm in volume. It is arranged singly or in pairs.

What does E coli look like on EMB Agar?

Escherichia coli appears as large, blue-black colonies, often with a green metallic sheen. … On EMB Agar (HHT), isolated colonies of lactose- and/or sucrose-fermenting coliforms will produce blue-black colonies with dark centers, often with a green metallic sheen. Other coliforms produce mucoid, pink colonies.

What type of media is EMB and why?

Eosin methylene blue agar (EMB) is a selective and differential medium used to isolate fecal coliforms. Eosin Y and methylene blue are pH indicator dyes which combine to form a dark purple precipitate at low pH; they also serve to inhibit the growth of most Gram positive organisms.

Is Mac selective or differential?

MacConkey agar (MAC) is a bacterial culture medium named after bacteriologist Alfred T. MacConkey (1861-1931). MacConkey agar is a selective and differentiating agar that only grows gram-negative bacterial species; it can further differentiate the gram-negative organisms based on their lactose metabolism.

Does E coli grow on MacConkey Agar?

MacConkey agar not only selects for Gram-negative organisms by inhibiting Gram-positive organisms and yeast but also differentiates the Gram-negative organisms by lactose fermentation. … Escherichia coli and other lactose ferments will produce yellow or orange colonies.

Why is MacConkey agar selective as well as 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. Lactose provides a source of fermentable carbohydrate, allowing for differentiation.

What makes EMB Agar differential?

Eosin Methylene Blue (or EMB) Agar is a Selective & Differential Medium. The selective and differential aspects are due to the dyes Eosin Y and Methylene Blue, and the sugars lactose and sucrose in the medium. It is Selective because it encourages some bacteria to grow while inhibiting others.

What is the differential agent in EMB?

EOSIN METHYLENE BLUE AGAREOSIN METHYLENE BLUE AGAR (EMB agar) Eosin methylene blue agar is a differential medium used for the detection and isolation of Gram-negative intestinal pathogens. A combination of eosin and methylene blue is used as an indicator and allows differentiation between organisms that ferment lactose and those that do not.

What is the difference between EMB agar and MacConkey Agar?

An example of a selective medium is MacConkey agar. It contains bile salts and crystal violet, which interfere with the growth of many gram-positive bacteria and favor the growth of gram-negative bacteria. … EMB contains the dyes eosin and methylene blue that inhibit the growth of gram-positve bacteria.