If you have gram positive cocci you have

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If you have Gram Positive Cocci, you have Streptococcus or Staphylococcus . Catalase (Atlas Page 63) “Does this Bacterium produce the Enzyme Catalase to break-down Hydrogen Peroxide?” Aerobic and Facultatively Anaerobic Bacteria produce Hydrogen Peroxide non- enzymatically as an unavoidable Side Product of Aerobic Respiration. Aerobic and Facultative Anaerobic Bacteria can also produce Hydrogen Peroxide enzymatically via the Enzyme Superoxide Dismutase: Hydrogen Peroxide is Bad News for Bacteria (which is why you use Hydrogen Peroxide to disinfect a Wound). So Bacteria that produce Hydrogen Peroxide usually produce the Enzyme Catalase to break it down to harmless Water and Oxygen Some Bacteria produce Hydrogen Peroxide but do not have the Enzyme Catalase. As a Result, Peroxides will accumulate and limit Colony Growth. You may have noticed that some Gram Positive Cocci tend to produce very small Colonies. The Catalase Test is insanely easy and fun. You’ll use a Sterile Toothpick to make a Smear and then add a Drop of Hydrogen Peroxide (Clear). If it fizzes and looks like Wombat Spit, then it’s Catalase Positive and it’s either Staphyloccus epidermidis or Micrococcus luteus . If it doesn’t fizz, then it’s Catalase Negative, and it’s Streptococcus lactis . Some of our Staphylococcus epidermidis will take up to 10 Minutes to fizz. So be very wary of Negative Catalase Results on any Unknown. Request a YGC Plate!
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Lab 6 Page 26 Gram Negative Biochemical Tests The Game Plan: You’ll do an Oxidase Test to determine whether your Bacterium is Pseudomonas or an Enteric. You’ll confirm Pseudomonas by plating on F Agar. You’ll then determine whether your Enteric is E. coli or Enterobacter by performing an IMViC (which is actually four separate Biochemical Tests). Oxidase (Atlas Page 87) “Does this Bacterium have the Enzyme Cytochrome Oxidase?” Aerobes, Facultative Anaerobes, and Microaerophiles have the Enzyme Cytochrome Oxidase in their Electron Transport Chains to transfer Electrons to Water. We’ll be checking for the Presence of this Enzyme by adding a reduced Artificial Electron Donor (Tetramethyl-p-Phenylendiamine). If Cytochrome Oxidase is present it will oxidize this Artificial Electron Donor and change it to a dark Blue. The Oxidase Test is fairly easy. Get a Piece of Filter Paper and use a Sterile Toothpick and transfer a large Goober of Bacteria. You want a large, visible Smear. Then add a Drop of the Oxidase Reagent (Light Blue). If your Bacterium is Oxidase Positive, the Goober of Bacteria will turn dark Blue (and it will do so within about 10 Seconds) . This means you have Pseudomonas . If your Bacterium is Oxidase Negative, the Goober will remain icky Latex Colored. This means you have an Enteric Bacterium, either E. coli or Enterobacter . However, keep in Mind that given sufficient Time -- say a few Minutes -- these Bacteria will also turn dark Blue.
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