Question: Which Agar Is Both Selective And Differential?

Why do we use LB agar?

Luria broth (LB) is a nutrient-rich media commonly used to culture bacteria in the lab.

The addition of an antibiotic to this gel allows for the selection of only those bacteria with resistance to that antibiotic – usually conferred by a plasmid carrying the antibiotic resistance gene..

Why is MacConkey Agar considered both differential and selective?

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.

Is chocolate agar selective or differential?

Chocolate agar, a differential medium for gram-positive cocci. Journal of Clinical Microbiology.

What bacteria can grow on EMB agar?

Some strains of Salmonella and Shigella may fail to grow on EMB Agar. Some gram-positive bacteria, such as enterococci, staphylococci, and yeast will grow on this medium and usually form pinpoint colonies. Non-pathogenic, non-lactose-fermenting organisms will also grow on this medium.

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 is MacConkey agar selective as well as differential quizlet?

Why is MacConkey agar selective as well as differential? It’s selective to gram negative enteric bacteria because it contains bile salts, which inhibit most gram positive bacteria. It also contains lactose, which differentiates between gram negative lactose fermenter and gram negative non-fermenters.

What is the difference between LB agar and LB broth?

LB agar is LB broth that contains agar and is typically prepared in petri dishes. … In the absence of antibiotics, LB agar is nutritionally rich, allowing the growth of most microorganisms. To prepare, agar is typically added to liquid LB, then autoclaved to produce a hot, liquid solution.

Is blood agar selective or differential or both?

Blood agar is a differential medium that distinguishes bacterial species by their ability to break down the red blood cells included in the media. Blood agar is often used to distinguish between the different species of pathogenic Streptococcus bacteria.

Is EMB Agar selective or differential?

EMB is a selective, differential agar medium used for isolation of gram negative rods in a variety of specimen types.

What does E coli look like on MacConkey Agar?

coli was made based on its characteristic morphology colony on the selective medium MacConkey agar. Rapid lactose fermenting colonies of E. coli appear dry, donut shaped and dark pink in color and are surrounded with dark pink area of precipitated bile salts.

What bacteria does not grow on blood agar?

Blood agar is an enriched, bacterial growth medium. Fastidious organisms, such as streptococci, do not grow well on ordinary growth media. Blood agar is a type of growth medium (trypticase soy agar enriched with 5% sheep blood) that encourages the growth of bacteria, such as streptococci, that otherwise wouldn’t grow.

Which media is both selective and differential?

MacConkey agar is an example of a medium that is both differential and selective. The presence of bile salts, as well as crystal violet, within the media prevent gram-positive organisms from growing.

Is mannitol salt agar selective or differential?

Mannitol Salt Agar (MSA) This type of medium is both selective and differential. The MSA will select for organisms such as Staphylococcus species which can live in areas of high salt concentration (plate on the left in the picture below).

Why is blood agar not a selective media?

Blood agar is an enriched medium that provides an extra rich nutrient environment for microbes. Therefore, BAP is not a selective growth medium, since it supports the growth of a wide range of organisms.

What is the difference between blood agar and chocolate agar?

The composition of chocolate agar and the Blood Agar is the same and the only difference is while preparing chocolate agar, the red blood cells are lysed. … Neither of these species is able to grow on sheep blood agar. Chocolate agar slants are used for the short-term storage of pathogens such as N.

Does E coli grow on chocolate agar?

Chocolate agar, however, does not reveal hemolysis data, so species differentiation among the members of Haemophilus must be performed in another manner. … This is an agar upon which only Gram-negative bacteria can grow. What is more is that E. coli will grow into red colonies, as there is a pH indicator present.

Is LB agar selective or differential?

There are a few types of general nutrient agar plates. Luria Bertani (LB) agar is a common nutrient agar for the general routine growth of bacteria and is not preferentially suited toward a particular microbe type.

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.

Is chocolate agar a selective medium?

Chocolate Agar supplemented with bacitracin is a selective medium used to improve the primary isolation of H. influenzae from specimens containing a mixed flora of bacteria and/or fungi.