MacConkey Agar

Eosin Methylene Blue Agar

Mannitol Salt Agar

Biochemical Testing involves giving microbes a type of molecule (also called substrate or nutrient) to see if the microbe produces enzymes that allow the microbe to use the substrate. There has to be some microbe used it. Proof can be an observation of growth or a change in color, based on the reaction between a product of metabolism of the substrate and an indicator chemical.

Catalase  How does the bacterium benefit from the production of this enzyme?  How do you test for the presence of this enzyme?  How do you know if the enzyme is present? What are the bubbles? Citrate UtilizationWhat nutrient is used to differentiate bacteria? 

negative  positive

Fermentation - Phenol Red Carbohydrate Utilization (Fermentation) Broth – Dextrose, Lactose, Mannitol 

negative  positive

Methyl Red (MRVP)

negative positive

Gelatin Utilization 

negative positive positive

Tryptophan Hydrolysis - Indole Production (Tryptone Broth 

negative positive

Hydrogen Sulfide Production (Kligler's Iron Agar)

negative positive

microorganism tests positive for H2S productionOxidaseFluid Thioglycollate Medium In the next block, sketch the expected area of growth for obligate aerobes, facultative anaerobes, microaerophilic bacteria, aerotolerant anaerobes, obligate anaerobes.

Antibiotic susceptibility – Kirby Bauer method 

Glucose Salts Agar (GSA): is a simple, defined medium.  Only organisms that can make all their cellular components from glucose and inorganic salts are able to grow on this medium.

Tryptic Soy Agar (TSA): is a rich, undefined medium containing products of an enzymatic digest of protein and soy product.  Organisms that require vitamins or other growth factors are able to grow on TSA.

Eosin Methylene Blue (EMB) Agar: is a selective AND a differential

medium.  The selective components are the eosin and methylene blue dyes that inhibit the growth of Gram-positive bacteria and permit the growth of Gram-negative enteric rods.  The differential component of the medium is lactose, which is a sugar that some organisms can ferment as an energy source.  Organisms that ferment lactose produce dark purple (sometimes shiny) colonies and those that cannot, produce white or very light pink

colonies.