Table of Contents
What ingredient in PEA supplies Nitrogen? Because they contain protein, casein, and soybean act as nitrogen sources.
What ingredients are in EMB Agar Supply Carbon?
What ingredient in EMB agar supplies Carbon? The sugars, lactose and sucrose.
What are the roles of crystal violet and bile salts?
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. Based on the ability to ferment lactose, different species will yield colonies in varying appearance on a MacConkey medium.
What type of media is pea agar?
Specifically, PEA agar is a selective medium that is used for the isolation of gram-positive Staphylococcus species and Streptococcus species from clinical specimens or specimens that contain mixtures of bacterial flora.
What grows pea agar?
Phenylethyl alcohol agar (PEA) is a selective medium used to cultivate Gram-positive organisms, particularly cocci, from a sample containing a mixture of pathogens. Staphylococcus aureus, a Gram-positive organism, grows on PEA while Serratia marcescens, a Gram-negative organism, does not.
What ingredients in EMB supplies nitrogen?
Gelatin is derived from the protein collage and is the sole source of nitrogen. EMB Test.
Is EMB defined or undefined?
Eosin methylene blue agar (EMB) is an undefined medium. EMB is a complex medium consisting of peptone, dipotassium phosphate, lactose, eosin Y (dye),.
What ingredients MacConkey agar supplies carbon and nitrogen?
It wouldn’t likely alter sensitivity because you would probably still be able to detect growth of organisms that “should” grow on it. 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 ingredients make MacConkey agar selective?
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. Fermentation of this sugar results in an acidic pH and causes the pH indicator, neutral red, to turn a bright pinky-red color.
How do you make MacConkey agar?
Preparation of MacConkey Agar Suspend 49.53 grams of dehydrated medium in 1000 ml purified/distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C. Mix well before pouring into sterile Petri plates.
What is pea agar?
PEA agar is a selective medium that is used for the isolation of gram- positive Staphylococcus species andStreptococcus species from clinical specimens or specimens that contain mixtures of bacterial flora (2). Typically PEA agar is used to inhibit the common contaminants such as Escherichia coli and Proteus species.
What is nutrient agar?
Nutrient agar consists of peptone, beef extract and agar. Beef extract contains water-soluble substances (carbohydrates, vitamins, nitrogen compounds and salts). Peptones are the main source of organic nitrogen, especially via amino acids and long-chain peptides. Agar is used as a gelling agent.
What ingredient makes this medium selective?
This medium is both selective and differential. The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria.
Are streptococci Gram positive?
Streptococci are Gram-positive, nonmotile, nonsporeforming, catalase-negative cocci that occur in pairs or chains.
Can Proteus grow on pea?
If used properly, PEA will support good growth of most anaerobes found in clinical infections. PEA should inhibit the growth of facultative anaerobic gram-negative rods, like Escherichia coli and swarming of Proteus mirabilis. Some strains of facultative organisms (which should be inhibited) may grow on PEA.
Is nutrient agar selective or differential?
1. Observe the growth and appearance of colonies on all plates. Notice that nutrient agar is neither a selective nor differential medium.
What is the carbon source in EMB?
Peptic digest of animal tissue serves as source of carbon, nitrogen, and other essential growth nutrients. Lactose serves as the source of energy by being the fermentable carbohydrate. Eosin-Y and methylene blue serve as differential indicators.
What is the purpose of EMB agar?
EMB agar is used in water quality tests to distinguish coliforms and fecal coliforms that signal possible pathogenic microorganism contamination in water samples.
Which molecule do indole positive bacteria cleave to form indole?
Indole is generated by reductive deamination from tryptophan via the intermediate molecule indolepyruvic acid. Tryptophanase catalyzes the deamination reaction, during which the amine (-NH2) group of the tryptophan molecule is removed. Final products of the reaction are indole, pyruvic acid, ammonium (NH4+) and energy.
Is agar defined or undefined?
Like other growth media, the formulations of agar used in plates may be classified as either “defined” or “undefined”; a defined medium is synthesized from individual chemicals required by the organism so the exact molecular composition is known, whereas an undefined medium is made from natural products such as yeast.
Would removing bile salts and or crystal violet from MacConkey?
How would removing crystal violet from MacConkey Agar alter the sensitivity and specificity of the medium? It would inhibit the growth of gram positive bacteria because this test is used to differentiate the gram positive bacteria and enterobacteria. What color is Gram +?.
Is mannitol salt agar defined or undefined?
Is MSA a defined or undefined medium? MSA is an undefined medium because the exact composition of beef extract and peptone are unknown. The goal of this medium is to isolate desired organisms, and once the undesired organisms have been inhibited, you want the desired ones to grow well.
What do deamination and decarboxylation have in common?
What do deamination and decarboxylation reactions have in common? They are both enzymes that catalyze the removal of amino acids groups. Purple= positive test that produces decarboxylation, organism produces the speific decarboxylation enzyme.
Is MacConkey agar defined or complex?
Nutrient broth, tryptic soy broth, and chocolate agar, are all examples of complex media. Selective media are used for the growth of only selected microorganisms. An example of a selective medium is MacConkey agar (Table 9.1 & Figure 9.26).
What type of medium is MacConkey agar?
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.
