Partial hemolysis is termed alpha-hemolysis.Staphylococcus aureus, Streptococcus pyogenes and Streptococcus agalactiae are b-hemolytic (the picture on the left below (transparent) zone surrounding the colonies. Members of the genera Staphylococcus, Streptococcus and The degree of hemolysis by these hemolysins is helpful in differentiating Hemolysins, enzymes that damage/lyse red blood cells (erythrocytes). BAP tests the ability of an organism to produce It is a rich, complex medium that containsĥ% sheep red blood cells. With an organism that can ferment lactose). a lactoseīroth tube that turns yellow after incubation has been inoculated The same results are considered positive (e.g. Indicator (phenol red) is also used in these fermentation tubes, *Note - broth tubes can be made containing sugars other than Notice that Shigella dysenteriae (far left) ferments glucose but does not produce gas. Mirabilis (far right) are both gas producers. This gas is trapped in the Durham tube and appears as a bubbleĪt the top of the tube. To H 2 (g) and CO 2 (g), via the action of the enzyme formic hydrogen lyase, emit Organisms that areĬapable of converting pyruvate to formic acid and formic acid The end product of glycolysis is pyruvate. Escherichia coli is capable of fermenting glucose as are Proteus mirabilis (far right) and Shigella dysenteriae (far left). If an organism is capable of fermenting the sugar glucose, thenĪcidic byproducts are formed and the pH indicator turns yellow. Like MSA, this medium also contains the pH indicator, phenol red. This is a test commonly used when trying to identify Gram-negativeĮnteric bacteria, all of which are glucose fermenters but only The end product of glycolysis, pyruvic acid into gaseous byproducts. To ferment the sugar glucose as well as its ability to convert While Staphylococcus epidermidis is not (right side of left plate). StaphylococcusĪureus is capable of fermenting mannitol (left side of left plate) The media will cause the pH indicator, phenol red, to turn yellow. Of fermentation that will lower the pH of the media. OrganismsĬapable of using mannitol as a food source will produce acidic byproducts The differential ingredient in MSA is the sugar mannitol. High salt agar (plate on the right in the picture below). Streptococcus species, whose growth is selected against by this 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). This type of medium is both selective and differential. Tests used to identify Gram Negative Bacteria Instructor can provide an uninoculated urea for comparison.Tests used to identify Gram Positive Bacteria.After 48 hours incubation, observe for ammonia production (basic conditions).Be sure to read about this test in Leboffe and Pierce!.If no color change develops, add a pinch of Zinc and note if the color changes.After 48 hours incubation, perform the test for nitrite as follows:.Alpha-napthylamine Reagent in dropper bottles Sulfanilic Acid Reagent in dropper bottles Instructor can bring out some uninoculated tubes for comparison. Also check to see if any gas has been produced. After 48 hours incubation, observe for acid production.Inoculate (stab) a set of carbohydrates with each organism.Use two tubes of each carbohydrate per group.Also the organisms from the starch and gelatin experiments Glucose Tubes (Phenol red broth) - 2 per group Since gelatin is liquid at 37 o C, gelatinase activity can be evaluated after 48 hours incubation by placing the tubes in the refrigerator for about 10 minutes.Check for the presence of starch which is indicated by the formation of a blue-black color.Įxperiment 2 - The Utilization of Gelatin Take a wooden applicator stick and scrape away some growth from each of the organisms so that the medium shows. After 48 hours incubation, flood the plate with gram's iodine.Spot the microbes in the center of the appropriate section:.Divide the plate into 4 equal sections labeled A, B, C, D.Experiments Investigating Exoenzymes, Carbohydrate Fermentation, Nitrate Reduction and Urea HydrolysisĮXPERIMENTS INVESTIGATING EXOENZYMES AND THEMAJOR FOOD GROUPS: STARCH HYDROLYSIS AND GELATIN HYDROLYSIS MATERIALSĪCTIVITIES Experiment 1 - The Utilization of Starch
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