Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Microbiology 211
Lab #42 - Physiological Characteristics: Hydrolytic and Degradative Reactions
| Question | Answer |
|---|---|
| Why are bacteria unable to surround and engulf their food by the process of phagocytosis? | Bacteria have rigid cell walls. |
| Phagocytosis is a characteristic of: | Higher cells. |
| How do bacteria acquire nutrients? | Bacteria excrete a variety of hydrolytic and degradative exoenzymes that degrade large macromolecules into smaller units that can be transported into the cell for metabolic purposes. |
| Which exoenzymes degrade starch and cellulose into simple sugars that are then transported into the cell where they are metabolized by fermentation or oxidation? | Amylase degrades starch, Cellulase degrades cellulose. |
| What type of exoenzyme degrades proteins such as casein and gelatin, and polypeptides into amino acids? | Protease |
| What type of exoenzyme degrades triglycerides into fatty acids and glycerol? | Lipase |
| Why do bacteria sometimes hydrolyze small molecules? | Because they can acquire carbon compounds for metabolic purposes. |
| Give an example of the hydrolysis of small molecules used to acquire carbon compounds for metabolic purposes. | Tryptophane is split into pyruvate and indole by the enzyme tryptophanase. The pyruvate is metabolized but the indole ring accumulates in the growth medium because it cannot be broken down. |
| The accumulation of ___ is the basis for a biochemical test that differentiates bacteria that produce tryptophanase from those that do not produce the enzyme. | indole |
| Some bacteria hydrolyze ___ to produce carbon dioxide and ammonia, thereby causing the pH to become alkaline. | Urea |
| The change in PH is detected by a color change in a __ ____. | pH indicator. |
| What kind of bacteria, in particular; can oxidatively deanimate phenylpyruvic acid? The latter (recently) can be detected with ____ ____. | Proteus (and other bacteria). Ferric chloride. |
| What can be used as a basis for identifying bacteria? | The presence of hydrolytic and degradative enzymes. |
| The starch macromolecule consists of two constituents: | Amylose and amylopectin. |
| Amylose | Straight chain polymer of 200-300 glucose molecules on the starch macromolecule. |
| Amylopectin | A large branched polymer of glucose on the starch macromolecule. |
| Bacteria that hydrolyze starch produce ____ that degrade the starch molecule into molecules of ___, ___, ___. | Amylases. Maltose, glucose, and dextrins. |
| How is starch hydrolysis detected? | By adding iodine to starch medium. Iodine complexes with the starch macromolecule and causes the medium to turn blue. |
| If the starch has been degraded, the medium adjacent to the bacterial growth will be ___ after the addition of the iodine. | Clear. |
| Which bacteria produces amylases that degrade starch? | Bacillus subtilis. |
| What materials are needed for the Starch hydrolysis test? | Gram's iodine and starch agar plates. |
| If starch is degraded, a ___ area will occur next to the growth of the organism. Areas on the plate where no starch hydrolysis has occurred will be ___. | Clear, blue. |
| What illustrates a positive starch hydrolysis result? (Positive amylase) | Clear zone along streak indicates starch hydrolysis. |
| What illustrates a negative starch hydrolysis result? (Negative amylase) | No clear zones along streak indicates that no hydrolysis of starch occurred. |
| Which bacteria tested positive for amylase in the Starch Hydrolysis Test? How can you tell? | Bacillus subtilis. (Clear zone) |
| Which bacteria tested negative for amylase in the Starch Hydrolysis Test? How can you tell? | S. aureus. (No clear zone) |
| ___ is the predominant protein in milk and its presence causes milk to have its characteristic white color. | Casein. |
| Many bacteria produce what kind of enzymes that degrade protein molecules such as casein into peptides and amino acids? | Proteases |
| Proteolysis | The process in which enzymes called proteases degrade protein moleculessuch as casein into peptides and amino acids. |
| What type of medium is used for the Casein hydrolysis test, and how can you indicate whether it has tested positive for caseinase? | Skim milk agar, the clear zone surrounding the bacterial growth shows where proteolysis of casein has occurred. |
| Which organisms tested positive for caseinase in the Casein Hydrolysis Test? | Bacillus subtilis and S. aureus. |
| What are fats (or triglycerides) composed of? | A glycerol molecule to which fatty acid molecules are covalently bonded through ester bonds. |
| Triglycerides | Primarily fat storage products in higher organisms such as animals. |
| Some bacteria produce enzymes called ___ that cleave the fatty acids from glycerol. What does this serve? | Lipases; so the fatty acids and glycerol can then be used for metabolic purposes such as synthesizing phospholipids for membrane construction or for catabolism to produce energy. |
| Why does butter or margarine become rancid? | The decomposition of triglycerides and the breakdown of the fatty acids into short chain volatile organic acids. |
| What medium is used for the Lipid (Fat) Hydrolysis test? What indicates a positive and negative result? | Spirit blue agar. Dark blue pigmentation on organism indicates it hydrolyzes fat, means that it is positive for lipase. Clear zone surrounding bacterial growth indicates that it does not hydrolyze fat, and means that it is negative for lipase. |
| Which organism tested positive for lipase in the Lipid (Fat) Hydrolysis Test? How can you tell? | S. aureus, dark blue pigmentation indicates that it hydrolyzes fat, which means it is positive for lipase. |
| Which organism tested negative for lipase in the Lipid (Fat) Hydrolysis Test? How can you tell? | Bacillus subtilis, it does not have dark blue pigmentation, instead it has a clear zone surrounding its growth; which means that it does not hydrolyze fat and therefore is negative for lipase. |
| What does Spirit blue agar used in the Lipid (Fat) Hydrolysis Test contain? | Peptone as a source of carbon, nitrogen, and vitamins. It also contains tributyrin, a simple natural animal triglyceride that serves as a substrate for lipases. |
| What is Tributyrin and where is it contained? | A simple natural animal triglyceride that serves as a substrate for lipases; found in Spirit Blue agar. |
| How does the dark blue precipitate occur in the Lipid (Fat) Hydrolysis Test? | Release of the fatty acids from tributyrin via lipase activity results in the lowering of the pH of the agar, causing the dark blue pigmentation. |
| Some bacteria do not completely hydrolyze all the fatty acids from the tributyrin, so what happens as a result in the Lipid (Fat) Hydrolysis Test? What would oil droplets indicate? | The pH is not sufficiently lowered to give a dark blue precipitate. In this case, all you notice may be simply the depletion of fat or oil droplets in the agar to indicate lipase activity (therefore, that would it is positive). |
| Some bacteria have the ability to degrade the amino acid ___, producing indole, ammonia, and pyruvic acid. What is the pyruvic acid can then be used for? | Tryptophan. Pyruvic acid can then be used for metabolic purposes. |
| What enzyme is responsible for the cleavage of tryptophan? | Tryptophanase. |
| How is the degradation of tryptophan by the enzyme detected? | Kovac's reagent, which forms a deep red color if indole is present. |
| What medium is used for the Tryptohanase Hydrolysis test? Why? Where is it derived from? | Tryptone broth (1%) is used for the test because it contains high amounts of tryptophan. Tryptone is derived from casein by a pancreatic digestion of the protein. |
| How would you test for indole and therefore the activity of tryptophanase in the Tryptophanase Hydrolysis Test? What should happen if it is positive for indole? | Add 10-12 drops of Kovac's reagent to the tryptone broth culture of E.Coli. A red organic layer should form on top of the culture (which is clear-yellowish). |
| Urea | Waste product of animal metabolism that is broken down by a number of bacteria. |
| What is the enzyme responsible for urea hydrolysis? | Urease, which splits urea molecules into carbon dioxide and ammonia. |
| How is urease produced? | By some of the gram-negative enteric bacteria such as Proteus, Providencia, and Morganella, which can be differentiated from other gram-negative enteric bacteria by the Urea Hydrolysis test. |
| What does the Urea agar slant medium contain? | Yeast extract, urea, a buffer, and the pH indicator phenol red. |
| Urea is unstable and is broken down under steam pressure at __ psi. | 15 |
| How is the urea medium prepared for the Urea Hydrolysis Test? | The urea medium is prepared by adding filter-sterilized area to the base medium after autoclaving it. |
| When urease is produced by an organism, the resulting ammonia causes the pH to become ____. | Alkaline. |
| As the pH increases, the phenol red indicator used in the Urea Hydrolysis Test changes from ____ to ___ or ____. | Yellow to bright pink, or cerise color. |
| In the Urea Hydrolysis Test, how can you tell that Proteus vulgaris was positive for urease production in the Urea agar slant? | Was yellow; then turned bright pink in the urea slant. |
| If your Urea slant is negative, what do you need to do? | Continue the incubation for an additional 7 days to check for slow urease production. |
| Which bacteria can oxidatively deaminate the amino acid phenylalanine to produce phenylpyruvic acid and ammonia? | Gram-negative bacteria such as Proteus, Morganella, and Providencia. |
| How is the phenylalanine deamination reaction catalyzed? | Catalyzed by the enzyme phenylalanine deamninase, a flavoprotein oxidase. |
| Phenylalanine deamninase | An enzyme, flavoprotein oxidase. |
| How can phenylalanine deamninase be detected? | By the addition of 10% ferric chloride, which forms a green colored complex with alpha-keto acids, such as phenylpyruvic acid. |
| How is the Phenylalanine Deamination Test useful? | To differentiate bacteria from other enterobacteriaceae. |
| The PPA Test (Phenylalanine deamninase) exhibits a positive reaction if it turns: | Green. |
| The PPA Test (Phenylalanine deamninase) exhibits a negative reaction if it turns: | Remains yellowish, colorless. |
| Gelatine Hydrolysis Test result: | Tube stayed liquid, positive for hydrolysis. |
Created by:
814152377