Quick Answer: Is Mannitol Salt Agar Selective Or Differential?

Which media is selective and differential?

Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms.

Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present..

What makes mannitol salt agar selective?

Mannitol Salt Agar (MSA) is a selective and differential medium. The high concentration of salt (7.5%) selects for members of the genus Staphylococcus, since they can tolerate high saline levels. Organisms from other genera may grow, but they typically grow very weakly.

What bacteria can grow on MacConkey Agar?

MacConkey agar is an indicator, a selective and differential culture medium for bacteria designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacilli and differentiate them based on lactose fermentation.

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.

Is nutrient broth selective or differential?

Nutrient broth, tryptic soy broth, and brain heart infusion, are all examples of complex media. Media that inhibit the growth of unwanted microorganisms and support the growth of the organism of interest by supplying nutrients and reducing competition are called selective media.

Is E coli catalase positive or negative?

coli, Enterobacter, Klebsiella, Shigella, Yersinia, Proteus, Salmonella, Serratia), Pseudomonas, Mycobacterium tuberculosis, Aspergillus, Cryptococcus, and Rhodococcus equi. If not, the organism is ‘catalase-negative’. Streptococcus and Enterococcus spp. are catalase-negative.

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.

Why is mannitol salt agar both selective and differential?

Mannitol salt agar or MSA is a commonly used selective and differential growth medium in microbiology. It encourages the growth of a group of certain bacteria while inhibiting the growth of others. … If an organism can ferment mannitol, an acidic byproduct is formed that causes the phenol red in the agar to turn yellow.

Is E coli a mannitol fermenter?

Gram-negative bacteria like E. coli and P. … Staphylococcus aureus is also able to ferment mannitol, because this bacterial species has the enzyme coagulase required for the process.

Is MacConkey agar selective or differential?

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.

Can a media be both selective and differential?

Selective and differential media can be combined and play an important role in the identification of bacteria by biochemical methods. Another commonly used medium that is both selective and differential is eosin-methylene blue (EMB) agar. … Therefore, EMB is selective for gram-negatives.

Is MacConkey agar 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.

Is blood agar selective or differential?

Blood Agar This medium can be made selective by the addition of antibiotics. This medium is differential because: Blood Agar tests for the production of hemolysin which breaks down red blood cells.

Is E coli lactose positive or negative?

E. coli are facultative anaerobic, Gram-negative bacilli that will ferment lactose to produce hydrogen sulfide.

Can 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.