Selective, Differential, Enrichment Media

Question 1

Definition of selective media

Answer 1

contains chemicals that prevent the growth of unwanted bacteria, without inhibiting the growth of the desired bacteria

Question 2

Definition of enrichment media

Answer 2

contain chemicals that enhance the growth of the desired bacteria. Other bacteria will grow, but the growth of the desired bacteria will be increased

Question 3

Definition for differential media

Answer 3

contain various nutrients that allow us to distinguish one bacteria from another based on how they metabolize or change the media with a waste product

Question 4

Phenolethyl Alcohol Agar (PEA) Selctive agents: Selects for: Results:

Answer 4

Selective agents: Phenoethyl Alcohol –> disrupts membranes, causes phosphorus to leak, stops DNA synthesis selects for: Gram (+) bactera Results: Growth= Gram (+), No Growth= Gram (-)

Question 5

Mannitol Salt Agar (MSA) Selective agents: Selects for: Differential Agents Differentiates between:

Answer 5

Selective agent: 7.5% Nacl Selects for: salt-tolerant bacteria (aka halophiles) Differential agents: Mannitol: fermentable sugar Phenol Red: pH indicator Acidic: yellow Neutral: Red Basic: shocking pink Differentiates Between: mannitol fermentor and non-mannitol fermenter Mannitol fermentor: yellow around growth Non-Mannitol fermentor: growth –> red or shocking pink

Question 6

MacConkey Agar (MAC) Selective Agents: Selects for: Differential Agents: Differentiates between:

Answer 6

Selective agents: -Bile salts: inhibit Gram (+) growth - Crystal violet: inhibits Gram (+) growth Selects for: Gram (-) bacteria Differential agents: -Lactose: fermentable sugar - neutral red: pH indicator -neutral or basic: colorless - acidic: red Differentiates between -lactose fermentor: colonies turn a shade of red -non-lactose fermentor: colonies remain colorless

Question 7

Eosine Methylene Blue Agar (EMB) Selective Agents: Selects for: Differential agents: Differentiates between:

Answer 7

Selective agents: -Eosin: inhibit Gram (+) growth -Methylene Blue: inhibit Gram (+) growth Selects for: Gram (-) bacteria Differential Agents: -lactose: fermentable sugar -Eosin and Methylene Blue: Differentiates between: -lactose fermentor: growth, colonies are dark purple or green metalic sheen -non-lactose fermentor: growth, colonies will be colorless/pink

Question 8

Blood Agar Plate (BAP) Enriched with: Differential agents: Differentiates between:

Answer 8

Enriched with: 5% defibrinated sheep blood Differential agents: 5% defibrinated sheep blood Differentiates between: -Beta-Hemolysis: complete hemolysis/ clear zone around colony -Alpha- Hemolysis: greenish, cloudy around colony, partial destruction -Gamme-Hemolysis: no hemolysis, no change around colony

Question 9

Beige Agar with purple stripe on the side

Answer 9

Phenoethyl Alcohol Agar (PEA)

Question 10

Red Agar, Brown stripe on plate

Answer 10

Mannitol Salt Agar (MSA)

Question 11

Dark red agar, red stripe on plate

Answer 11

Eosine Methylene Blue Agar (EMB)

Question 12

Red agar, blue stripe on plate

Answer 12

MacConkey Agar Plate (MAC)

Question 13

Red agar, Blood agar label on lid

Answer 13

Blood Agar Plate (BAP)