Lab Quiz 3 Flashcards
What does EMB medium differentiate?
Degree of lactose fermentation
What kind of medium is Eosin Methylene Bromide?
Differential, Selective, Undefined
What does EMB medium select for?
Encourages Gram - growth
What is a color form bacteria?
A rod shaped, gram negative, lactose fermenter
What bacteria showed the highest degree of lactose fermentation?
E. coli, showed a green metallic color.
What is a strict anaerobe?
Can only survive without oxygen. Will only grow deep in agar.
What is a Facultative Anaerobe?
Can survive in both environments, aerobic and anaerobic
What is an Aerotolerant Anaerobe?
Thrives in anaerobic but can survive in aerobic
What are microaerophiles?
Survive in small oxygen concentrations only
What are strict aerobes?
Can only survive in aerobic environments
What does the Fluid Thiogycolate Medium test for?
Growth in different oxygen concentrations
What does the anaerobic container system test?
Growth in anaerobic conditions
How does the anaerobic container work?
Pump H2 gas into the chamber to produce water with oxygen in the tank. The water condenses in plastic around the chamber.
What is an acidophile?
Grows in acidic conditions
What is a neutrophils?
Grows in neutral environments
What is an alkaliphile?
Grows in basic environment
Why do you out a buffer in broth when you are testing for growth in various pH?
Helps keep pH constant in the range for optimal bacterial growth
What is hypotonic?
Higher ion concentration inside of the cell. Will result in an influx of water into the cell.
What is hypertonic?
Lower ion concentration induce the cell. Result in rush of water out of the cell
What does the Phenol Red Broth test for?
Fermentation or Deamination
What does it mean if a Phenol Red Broth turns yellow?
Bacteria is positive for fermentation. Fermentation causes release of organic acids which lower the pH of the broth. Phenol Red is Yellow in acidic environments
What does it mean if a Phenol Red Broth stays red?
Bacteria is negative for fermentation. Phenol Red is Red in neutral pH. No acid was released in the medium
What does it mean if a Phenol Red Broth turns pink?
Bacteria is positive for deamination. When the bacteria breaks down proteins in the broth it releases ammonia, which is basic. Phenol red is Pink in basic environments.
What are the three sugars we tested for fermentation?
Glucose, Lactose and Sucrose
What are the three potential products of fermentation?
organic acids, alcohol, gas production
Is fermentation an anaerobic or aerobic process?
Anaerobic
What did the Catalase reactions test?
If bacteria contained catalase to break down hydrogen peroxide
How was the presence of catalase tested?
Observation of bubbles
What was tested during the Nitrate Reduction Test?
Presence of nitrate reducing enzymes
What did it mean if there was gas in the Nitrate Reduction Test?
Nitrogen gas was produced. The bacteria broke down nitrate with nitrate reductase and produced nitrogen gas by denritification.
What did it mean if the Nitrogen Reduction Test showed presence of NO2 (nitrite) after the addition of Reagents A and B by turning red?
The bacteria has nitrate reductase.
What did it mean if the Nitrogen Reduction Test showed presence of NO3 (nitrate) after the addition of zinc by turning red?
The bacteria has no nitrate reductase. The nitrate was left in the sample in it’s original form.
What did it mean if the Nitrogen Reduction Test result showed a colorless sample?
The bacteria had transformed all of the nitrogen into other gaseous products like N2O, NO, or NH3
What is the Sulfur-Indole-Motility (SIM) Test used for?
To test for three bacterial activities: sulfur reduction, indole production from tryptophan and motility.
What to enzymes can reduce sulfur in bacteria?
Cystein desulferase which uses sulfur to create pyruvate and hydrogen sulfide and Thiosulfurate reduction which reduces sulfur to hydrogen sulfide.
How do you know if the SIM Test shows sulfur reduction?
Black precipitate throughout the test tube
How is indole produced in bacteria?
Bacteria that possess the enzyme tryptophanase can hydrolyze tryptophan in the medium to create indole.
How is indole production shown in the SIM Test?
When Kovac’s reagent is added the top of the sample turns red.
How is motility tested for in the SIM Test?
If the bacteria is able to grow throughout the agar and not just in the stab it is motile
What do hydrolysis reactions do?
Use Hydrolytic enzymes and water molecules to break bonds
What are intracellular enzymes?
Enzymes that exist in the cell and act on molecules that enter the cell
What are extracellular enzymes?
Enzymes that diffuse into the medium from the cell. Act on molecules that need to be broken down before they can enter the cell
What is an example of an intracellular enzyme?
Urease
What is an example of an extracellular enzyme?
Amylase, Cesease, Lipase
What does the Casein Hydrolysis test for?
Bacterial possession of casease enzyme that breaks down casein protein in milk
How do you know if the Casein Hydrolysis test is positive?
Clearing in the medium around bacterial growth.
What does the Starch Hydrolysis test for?
Presence of amylase
What does amylase do?
Cleaves 1,4 alpha glycosidic linkages in starch molecules
How do you know if Starch Hydrolysis test is positive?
Clearing in the medium around bacterial growth. Detected by addition of iodine to medium.
What does Urea Hydrolysis test for?
Presence of urease
What does Urease do?
Cleaves urea into ammonia and CO2
What is the indicator in the Urea Hydrolysis test?
Phenol Red
Explain a Pink result of a Urea Hydrolysis test:
Rapid urea hydrolysis created a basic environment due to large amounts of ammonia produced. Bacteria has strong urease production. Basic environments are indicated by a pink color.
Explain a Red/Pink result of a Urea Hydrolysis test:
Slow urea hydrolysis created a slightly basic environment due to small amounts of ammonia produced. Bacteria has a weak urease production.
Explain a Yellow/Orange result of a Urea Hydrolysis test:
No urea hydrolysis. The Phenol Red indicator is detecting an acidic environment as the bacteria produce an acidic environment through their general growth and existence. No urease production.
What does the Lipid Hydrolysis test?
Bacterial possession of lipase
What does lipase do?
Breaks down triglycerides into glycerol and 3 fatty acids
How do you know if the Lipid Hydrolysis test is positive?
Clearing around bacterial growth.
