Microbiology Lab Quiz #4
How does amylase hydrolyze starch?
It breaks the bonds between the glucose chains.
What is an exoenzyme?
It is an extracellular enzyme that bacteria secret in order to break down and hydrolyze macromolecules.
What is a starch?
A large polymer made up of units of glucose.
What is starch used for?
Energy storage in plants and many microbes.
What is the exoenzyme of starch?
How does amylase work?
It diffuses away from the microbe and clears the starch outside of the cell.
What is the indicator used in starch hydrolysis?
What is a positive result for starch hydrolysis?
There will be a clear zone because the starch has been ingested and is no longer there. The iodine can not stick to what is not on the plate.
What is a negative result for starch hydrolysis?
There will be a blue/black complex because Gram's iodine will stick to the stain and dye it.
What type of plate is the bacteria added to for observing starch hydrolysis?
What are the end products of starch hydrolysis?
Dextrin and maltose
Starch is a special type of carbohydrate called
What is the purpose of a control?
To see if any changes are appearing on the testing for hydrolysis. The control should always be a negative result to compare against other negative results.
The detection of enzymatic activity on starch
is based upon the disappearance of the starch
The specific amylase, glucoamylase results in the end product
What is a lipid?
a large polymer made of fatty acids and glycerol; sometimes complexes with phosphate, nitrogen and sulfur
What type of media is used for lipid hydrolysis?
Spirit Blue Agar
An important property of lipids in the presence of water
They are hydrophobic.
What is the exoenzyme secreted by bacteria in lipid hydrolysis?
What is a positive result for lipid hydrolysis?
There will be a more intense blue color that forms around or under bacterial growth due to the release of fatty acids and the uptake of spirit blue.
What is a negative result for lipid hydrolysis?
There is no color change on the media is present.
Another term for lipid hydrolysis
What is the dye in the agar that serves as the indicator of lipolytic activity?
A lipase produced by C. perfringens causes ______ of RBCs by removing ________________ from certain membrane lipids.
lysis and phospholipids
What is a protein?
large polymer made up of repeating units of amino acids
What is the class of enzyme that hydrolyzes proteins into small fragments?
What is important about proteases?
They are specific to a particular substrate or for a specific amino acid sequence.
Process of protein hydrolysis is called
Proteolysis or peptonization
What type of agar is used in gelatin protein hydrolysis?
What is the protease that hydrolyzes gelatin protein?
What is the method used in gelatin protein hydrolysis?
Fraser overlay method
What is a positive result of gelatin protein hydrolysis?
No white precipitate forms upon being acidified because the protein has been digested by the bacteria and is no longer present.
What type of indicator is used in determining gelatin protein hydrolysis?
What is a negative result of gelatin protein hydrolysis?
White precipitate forms upon being acidified because acid denatures proteins and causes the white precipitate to form meaning that the protein is on the plate and has not been ingested by the bacteria.
At room temperature, gelatin is
Gelatin is derived from the animal substance
Using the plate overlay method, what indicator is added?
acidified mercuric chloride
The tube method of gelatin hydrolysis is less sensitive than
the Fraser overlay method.
Collagen degradation is detected by the release of a
Gelatinase activity results in the disappearance
of the gelatin
What is the protease that hydrolyzes the milk protein, casein?
What type of media is used in casein protein hydrolysis?
Skim milk agar
What is a positive result for casein protein hydrolysis?
Milk agar plate appear clear around the colony because the casein is ingest so there is no more cloudy milk appearance.
What is a negative result for casein protein hydrolysis?
Milk agar plate appears cloudy around the colony.
Casein is a protein
found in milk
Term used to describe casein hydrolysis specifically
The colloidal nature of milk serves as
the basis for interpreting casein hydrolysis
A special chemical reagent
is not added to test for casein protein hydrolysis
What is a nucleic acid?
Large polymers of nucleotides that can be RNA or DNA
The enzyme produced by bacteria that can break down nucleic acids to use the energy stored in those polymers in order to metabolize
What type of media is used in determining nuclease activity?
Agar plate with DNAse
What are the two methods used for detecting nuclease activity?
Inoculated test plate developed with HCL and Toluidine Blue Agar plate
What is a positive result for DNA hydrolysis on the inoculated plate with HCL?
Clear zone because nucleic acid is hydrolyzed.
What is a positive result of DNA hydrolysis on a Toluidine Blue Agar Plate?
Pink/red zone and clear area surrounds the colony of bacteria
What is a negative result of DNA hydrolysis on a Toluidine Blue Agar Plate?
No color change or change in appearance of the blue agar plate.
What is the bacteria that causes food poisoning?
What is the media used in blood hemolysis?
5% sheep blood agar
What are the exoenzymes that destruct red blood cells and hemoglobin?
What are the three terms used to describe hemolysis?
Alpha, beta and gamma hemolysis
What is Alpha Hemolysis?
partial destruction of RBCs and hemoglobin; cloudy/green zone around the colony
What is Beta Hemolysis?
complete destruction of RBCs around bacteria and hemoglobin is discolored. Clear zone around colony
What is Gamma Hemolysis?
Non-hemolysis; no change in the media because no RBC/hemoglobin destruction
Hemolysis is best observed
against a light background
What are the end products of protein hydrolysis
peptones and amino acids
What are the end products of lipid hydrolysis?
fatty acids and glycerol
Alpha-amylase cleaves starch to
oligosaccharides, maltose and glucose
Beta-amylase cleaves starch to
dextrins and maltose
Glucoamylase cleaves starch to
What is another term for lipases?
Once inside the cell, fatty acids can be used for
energy or building blocks for biosynthesis
Bacteria forming exonucleases can
utilize the carbon, nitrogen and end products of large polymers of RNA or DNA
What is thermostable mean?
a nuclease, bacteria can secrete that withstands boiling temperatures
Why is the thermostable property useful in identitying S. aureus food poisoning organisms?
When heating has destroyed the organisms but the nuclease is still present.
Pathogenic strains of streptococci are