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what is the difference between a mixed and a pure culture?
- Pure culture: contains only a single species
- mixed culture: microbial culture consisting of 2 more species
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What type of medium are you using in the streak plate methods of isolation exercise?
agar nutrient plate
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how many types of bacteria cells should be in an isolated bacterial colony?
In the streak plate method of isolation, a bacterial sample (always assumed to be mixed) is streaked boer the surface of a plated agar medium. During streaking the cell density decreases, eventually leading to indidual cells being deposited separetly on agar surfaces
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what is the one way to describe shape of bacterial conlony?
- round
- irregular
- punciform (tiny, pinpoint)
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what is one way to describe the elevation of the bacterial colony?
- convex
- umbnate
- plaeau
- flat
- raised or raised w/ spreading edge
- flat, raised, margin
- growth into medium
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In additon to shape and elevation, what is another way to describe colony morphology?
- Margin: smooth, undulate (wavy), lobate (lobed), filamentous or rhizoid (branched)
- Texture: moist, mucoid, dry
- pigment production: slightly dull, opaque, translucent, color
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whats the difference between a plate and a slant?
- plate: agar
- slant: tube w/ medium in it
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what is one way to describe a bacterial culture grown in broth?
- pellicle: float on the top of the medium
- sediment: sinks to the bottom
- flocculent: clump
- uniform fine turbidity: same through-out
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what is observed w/ the deep agar stabs?
oxygen tolerance
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how long are your cultures to stay in the incubator?
24-48 hours
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why is it necessary to stain cells before observing them?
so you can see it better
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how do ou "fix" the bacteria to the slide before you begin the process of staining?
heat fixing
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in the gram stain which stain is first, crystal violet or safranin?
crystal violet
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in the gram stain, after which step is the alcohol/decolorizer added?
after you add iodine
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what color is gram - cell wall when the process is done?
purple
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what is a defining chacteristic of acid-fast cells?
hard to get stain in because its waxy
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what is used to get the stain into the cell walls of acid-fast organisms?
heat
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Desoxycholate agar
inhibits gram + organism; bacteria colonies will turn pink if the carb. is fermented
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endo agar
inhibits gram +; lactose fermentors that produce high amounts of acid will yeild colonies w/ a gold metallic sheen
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Eosin Methelene blue agar
inhibits gram positive organisms while encourgaes the growth of fecal coliforms; can yeild colonies w/ green metalic sheen
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Hektoen Enteric agar
selects for salmonella and shigella speices
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macconkey agar
inhibits gram + organisms; medium contains bile salts and crystal violet; colonies of lactose fermentors turn red
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Manitol salt agar
selects for staphyloccoci; red medium turns yellow for pahtogenic organisms
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nutrient agar
serves as a growth control
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phenyltheyl alchol agar
selects for gram + and inhibits gram - organims by inergering w/ DNA synthesis
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what is the purpose of the durham tube?
gas
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why were there different types of phenol-red broths?
sugar
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name one carbon source that was tested for its capacity to support bacterial growth?
sugras- lactose, glucose, sucrose and citrate
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in reference to the fact that there is almost always an "indicator" included in a medium, what purpose does the uninoculated control serve?
grwoth control and comparison
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what chemical will you use to perform the catalse test?
hydrogen peroxide
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what is the indicator that an organims is catalase +?
bubble/gas
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