Term
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Definition
| a polysaccharide made up of alpha-D-glucose subunits |
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Term
| What are the 2 forms that starch can exist in and how do they differ? |
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Definition
-linear (amylose)
-branched (amylopectin)
they differ in that amylopectin contains polysaccharide side chains connected to approximately every 30th glucose in the main chain |
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Term
| What are alpha-amylase and oligo-1,6-glucosidase and why are they needed? |
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Definition
| extracellular enzymes that are secreted by organisms that are able to hydrolyze starch by breaking the glycosidic linkages between sugar subunits, since starch is too large to pass through bacterial cell membrane |
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Term
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Definition
| simple plated medium of beef extract, soluble starch, and agar |
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Term
| Why is the reagant iodine used in the starch agar? |
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Definition
| because start and its sugar subunits are invisible, so iodine is used to detect presence/absence of starch around bacterial growth |
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Term
| What does clearing around growth in the starch agar mean? |
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Definition
| amylase is present, starch was hydrolyzed by bacteria |
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Term
| What does no clearing around growth on the starch agar indicate? |
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Definition
| no amylase is present, no starch was hydrolyzed by bacteria |
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Term
| For bacteria to ferment lactose, what 2 enzymes must they possess? |
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Definition
| beta-galactoside permease and beta-galactosidase |
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Term
| beta-galactoside permease |
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Definition
| a membrane-bound transport protein needed for bacteria to ferment lactose |
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Term
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Definition
| intracellular enzyme possessed by bacteria that hydrolyzes lactose into beta-glucose and beta-galactose |
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Term
| What are late lactose fermenters? |
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Definition
| bacteria that possess beta-galactosidase but not beta-galactoside permease and mutate over a period of days or weeks to eventually produce permease |
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Term
| How do you distinguish late lactose fermenters from nonfermenters? |
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Definition
| by ONPG, which can enter bacteria without aid of permease and is similar to beta-lactose, so can act as a substrate for any beta-galactosidase present |
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Term
| What does yellow color formation in the ONPG test indicate? |
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Definition
| organism produces beta-galactosidase |
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Term
| What does not color change in the ONPG test indicate? |
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Definition
| organism does not produce beta-galactosidase |
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Term
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Definition
| a product of decarboxylation of certain amino acids |
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Term
| How do bacteria use the enzyme urease? |
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Definition
| to hydrolyze urea to ammonia and carbon dioxide |
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Term
| Why was urea agar formulated? |
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Definition
| to differentiate rapid urease-positive bacteria from slower urease-positive and urease-negative bacteria |
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Term
| What are the components of urea agar? |
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Definition
| urea, peptone, potassium phosphate, glucose, and phenol red |
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Term
| What is the purpose of peptone and glucose in urea agar? |
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Definition
| to provide essential nutrients for a broad range of bacteria |
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Term
| What is the purpose of potassium phosphate in urea agar? |
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Definition
| it is a mild buffer to resist alkalinization of the medium from peptone metabolism |
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Term
| What is the indicator used in urea agar? |
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Definition
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Term
| What color is phenol red below pH 8.4? above? |
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Definition
below-yellow or orange
above-red or pink |
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Term
| How does urea broth differ from urea agar? |
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Definition
-its only nutrient source is trace yeast
-it contains buffers strong enough to inhibit alkalinization of the medium by all but the rapid urease-positive organisms |
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Term
| What does all pink urease agar within 24 hours indicate? |
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Definition
| rapid urea hydrolysis, strong urease production |
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Term
| What does partially pink urease agar after 24 hours and all pink or partially pink agar after 6 days indicate? |
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Definition
| slow urea hydrolysis; weak urease production |
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Term
| What does orange or yellow urease agar after 24 hours and all pink or partially pink agar after 6 days indicate? |
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Definition
| slow urea hydrolysis; weak urease production |
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Term
| What does orange or yellow urease agar after 24 hours and still orange or yellow agar after 6 days indicate? |
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Definition
| no urea hydrolysis; urease is absent |
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Term
| What does pink urease broth indicate? |
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Definition
| rapid urea hydrolysis; strong urease production |
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Term
| What does orange or yellow urease broth indicate? |
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Definition
| no urea hydrolysis; organism does not produce urease or cannot live in broth |
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Term
| How is the urease test used in the real world? |
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Definition
| used to distinguish urinary tract pathogens of the genus Proteus from other enteric bacteria by their rapid urease activity |
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