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lab practical 2 blinn microbiology
Terms in this set (70)
What type of media is Nitrate Test?
Tests if bacteria has enzyme nitrate reductase
What is the purpose of the Nitrate Test?
to determine the ability of an organism to reduce nitrate (NO3) to nitrite (NO2) using the enzyme nitrate reductase. It also tests the ability of organisms to perform nitrification on nitrate and nitrite to produce molecular nitrogen.
What are the reagents used in nitrate test
What type of media is Motility test
Tests for bacterial movement and respiratory
Reagent used in Motility Test
Triphenyltetrazolium Chloride aka TTC
what are 3 rapid tests?
What type of media is Catalase Test?
presence of enzyme catalase
breaks down hydrogen peroxide into H2O and O2
Why is catalase test differential?
used to differentiate staphylococci (catalase-positive) from streptococci (catalase-negative)
What are the reagents used in catalase test?
What are you looking for a catalase test
bubbles of oxygen
What type of media is Mannitol Salt agar?
selective and differential
Why do we use MSA?
If an organism can ferment mannitol, an acidic byproduct is formed that will cause the phenol red in the agar to turn yellow
To identify pathogenic gram positive staphylococci
Ex. S. Aureus
What is the substrate used in MSA?
End Products observed in MSA?
fermented mannitol resulting in acid
What type of media is coagulase test?
Why is coagulase a differential media?
used to differentiate Staphylococcus aureus (G-positive) from Coagulase Negative Staphylococcus (CONS).
What is a coagulase?
Coagulase is an enzyme produced by S. aureus that converts (soluble) fibrinogen in plasma to (insoluble) fibrin
What is the reagent/substrate used in coagulase test?
reagent is rabbit plasma
Blood agar is a medium that is both what?
enriched and differential
Blood agar contains what to help many bacteria grow well on it?
Iron and other extra nutrients. Containing 5 % to 10 % sheep blood used most often.
The ability to break down blood cells (or not) makes this medium what?
Streptococcus and staphylococcus both make toxins called what? That do what?
hemolysins that can break RBCs.
Alpha-hemolysins cause partial lysis of RBCs, which leads to what?
what is alpha hemolysis
darkening of blood around the colony
What causes the green color often seen in alpha hemolysis?
complete lysis of the RBCs and breakdown of hemoglobin, which leads to colorless clearing of the blood agar around the colony.
If an organism causes no hemolysis, it is reported as what?
What is the cause of streptococcus pyogenes?
bacterial pharyngitis, or "strep throat"
streptococcus pneumoniae will cause
Enterococcus faecalis will cause
Alpha-hemolysis will appear as
a "halo"or partial clearing around the bacteria.
Gamma hemolysis will show as
no change at all in the blood around the bacteria. The bacteria are growing but not making anything to damage the blood.
detects bacteria that produce cytochrome c oxidase
what type of media is oxidase test?
reagent used in oxidase test
Results for Oxidase test
(+) Cytochrome oxidase is present : Violet or purple color (E.g. Neisseria species)
(-) No cytochrome oxidase : no color change
what is the application of MacConkey Agar Test?
used to isolate and differentiate members of the Enterobacteriaceae based on the ability to ferment lactose
What is the media of MacConkey Agar?
What is the purpose of Lactose in MacConkey agar?
detection of fermentation
What is the purpose of Bile salts and crystal violet in MAC?
it inhibits growth of Gram positive bacteria
What is the purpose of Neutral red in MAC?
a dye that is a pH indicator & is colorless above pH 6.8 and red at a pH less than 6.8
Coliforms are observed when
pink to red growth with or w/o bile precipitate, organism produces acid from lactose fermentation
Mac is (Gram Positive or Negative)?
Why do we use Triple Sugar Iron Agar test?
to differentiate members of Enterobacteriacea and to distinguish them from other gram- rods
TSIA is a type of what media?
What are the reagents/substrate used in TSIA?
glucose, lactose & sucrose animal protein
In TSIA, What is the purpose of glucose, lactose & sucrose?
source of carbon & nitrogen
In TSIA, what is the purpose of animal protein?
source of carbon and nitrogen
In TSIA, what is the purpose of ferrous sulfate?
source of oxidized sulfur & hydrogen sulfide indicator
What is the purpose of Ferrous sulfate?
In TSIA, what is the purpose of phenol red?
In TSIA, a sulfur rxn is observed by?
black precipitate in the agar
In TSIA, cracks and lifting is observed as ?
What type of media is urease test?
What is the purpose of the urease test?
used to detect the presence of the enzyme urease
What are the media found inside urease test?
What are the results for urease test?
positive =red/hot pink
negative = yellow
what type of media is Indole test?
Why is indole test differential?
to determine the ability of the organism to convert tryptophan into indole
Indole test by products are?
Reagent used in indole test?
Results for indole test?
Positive = red ring
negative = yellow ring
What is indole?
It is a waste product that is made when Tryptophanase breaks Tryptophan down. In high concentrations it smells like feces, but at lower concentration it smells like flowers.
What is the enzyme detected in the process of indole test
What is the substrate used in Indole Test?
Methyl Red test is a type of what media?
what does methyl red test for?
detects presence of long term stable acid products
What are the main ingredients in MR-VP broth?
-Methyl Red (for MP test)
-VP Reagents (for VP test)
What does the Methyl Red do in the MR-VP broth?
It is a Dye that indicates pH after Mixed Acid Fermentation, being added after incubation.
What are the reagents for Voges-Prokauer test?
What is the application of MR and VP test?
They are components of the IMViC battery of tests used to distinguish between members of the family Enterobacteriaceae and differentiate them from other Gram-Nagative Rods.
What steps were performed in the MR-VP test?
1. Inoculate 1 tube containing MR-VP broth with pure culture
2. Incubate for 48 hours
3. Transfer 1.0 mL of broth to 2 Nonsterile test tubes
4. Add 3 Drops of Methyl Red to one and read results immediately.
5. Add 15 drops of Naptha Alpha and mix; Add 5 Drops of KOH and mix well to Oxygenate.
6. Read results at 10 Minute intervals for 60 minutes.
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