25 terms

Microbiology Lab Review for test 3

Durham tube sugar Fermentations
Media/reagent used = Glucose durham tubes // End Product = acid or a gas // Positive indicator turns yellow and if gas production has bubble in the middle glass tube
Oxidase production
Media/reagent used = TSA plate / oxidase reagent // End Product/ Enzyme Checks for production of the enzyme oxidase // Positive indicator development of blue black around the edges indicates presence of oxidase
Mixed acid (Methyl Red)
Media/reagent used = MR-VP tube/ methyl red //End Product/ Enzyme mixed acid // a red color indicates a positive MR test //
Nitrate reduction
Media/reagent used = tube of nitrate broth/ Trommsdorf solution, H2SO4 // End Product/ Enzyme tests the ability of the bacteria to use nitrate as an electron acceptor // if mixture turns blue then NO2 is present and reduction test is positive - if does not turn blue then continue testing for presence of NO3 - Media/reagent used tube of nitrate broth/ diphenylamine, H2SO4 // if blue color develops then NO3 is present and test is negative - if does not turn blue, then nitrate reduction test is positive.
Starch Hydrolysis
Media/reagent used = starch agar plate/ Gram's iodine // End Product/ Enzyme Production of amylase // a colorless area surrounding the colony indicates the hydrolysis of starch= positive
Casein hydrolysis
Media/reagent used - Casein agar plate End Product/ Enzyme = caseinase /Production of caseinase // a clear zone around the colony indicates the break down of casein
Fat Hydrolysis
Media/reagent used = Peanut oil agar/ Neutral red indicator // End Product/ Enzyme = Production of lipase // positive it will turn bright pink which indicates lipid hydrolysis if stays brown - negative
Tryptophan Hydrolysis
Media/reagent used = Tryptone broth/ Kovac's reagent End Product/ Enzyme = Tryptophanase // positive formation of red ring
Butanediol Production (Voges-Proskauer test)
Media/reagent used = MRVP tube/ a-napthol, KOH with creatine // if red color develops test is positive for acetoin (butanediol) production
Urea Hydrolysis
Media/reagent used = Urea Agar slant // End Product/ Enzyme = Urease // Postive result = color change to pink
Gelatin Hydrolysis
Media/reagent used = Gelatin Agar plate/ Gelatin developer // End Product/ Enzyme = Gelatinase // Positive result = clear spot around colony // Negative result cloudy around colony
Hydrogen Sulfide production
Media/reagent used = SIM tubes (Sulfide-Indole-Motility) / Kovac's reagent // End Product/Enzyme = sulfate reduction no one enzyme // Positive agar turns black around the stab mark / shows motility if feathering away from stab mark
Citrate Utilization
Media/reagent used = Simmon's citrate agar slants / pH indicator bromthymol blue // End Product/Enzyme = no one enzyme // Positive result turns blue
Litmus Milk reaction
Media/reagent used = Litmus milk tubes // Alkaline reaction - turns purple or blue because of ammonia release that raised the pH to an alkaline level // Acid Reaction - turns pink becaue of fermentation of the milk sugars that cause an acidic condition // Litmus Reaction - become white from reduction of the litmus dye due to a drop in oxygen levels or because the bacteria using it as an alternative electron acceptor // Coagulation - curd formation from precipitation and coagulation of proteins // Peptonization - become translucent often turning brown due to degraded milk proteins // Ropiness - formation of thick slime
Phenylalanine deamination
Media/reagent used = Phenylalanine agar slants / iron chloride // End Product/Enzyme = Phenylalanase // Positive result - turns green
What is the most important single source of information we have for the identification of bacteria?
Use of Bergey's Manual of Systematic Bacteriology which catalogues characteristics of bacteria
Name of the apparatus used to test antimicrobics?
What are antimicrobials?
Antimicrobials inhibit or kill microorganisms and are usually chemically synthesized
What are antibiotics?
Antibiotics are compounds, usually of low molecular weight and produced by microorganisms, that inhibit or kill other microorganisms
What is the name of the agar used in this test?
Mueller-Hinton II agar
What factors influence the sphere of inhibition of an antimicrobic?
diffusibility of the agent, the size of the inoculum, the type of medium, and many other factors
What is an antiseptic?
A chemical agent that is used to control microorganisms on the skin or tissue
What is the difference between an antiseptic and a disinfectant?
antiseptic can be used on the skin and disinfectants are more harsh and can only be used on surfaces or objects
What factors influence the effectiveness of an antiseptic?
What method is used to test antiseptics?
Kirby-Bauer techinique