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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
What type of medium are you using in the streak plate methods of isolation exercise?
agar nutrient plate
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
what is the one way to describe shape of bacterial conlony?
- punciform (tiny, pinpoint)
what is one way to describe the elevation of the bacterial colony?
- raised or raised w/ spreading edge
- flat, raised, margin
- growth into medium
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
whats the difference between a plate and a slant?
- plate: agar
- slant: tube w/ medium in it
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
what is observed w/ the deep agar stabs?
how long are your cultures to stay in the incubator?
why is it necessary to stain cells before observing them?
so you can see it better
how do ou "fix" the bacteria to the slide before you begin the process of staining?
in the gram stain which stain is first, crystal violet or safranin?
in the gram stain, after which step is the alcohol/decolorizer added?
after you add iodine
what color is gram - cell wall when the process is done?
what is a defining chacteristic of acid-fast cells?
hard to get stain in because its waxy
what is used to get the stain into the cell walls of acid-fast organisms?
inhibits gram + organism; bacteria colonies will turn pink if the carb. is fermented
inhibits gram +; lactose fermentors that produce high amounts of acid will yeild colonies w/ a gold metallic sheen
Eosin Methelene blue agar
inhibits gram positive organisms while encourgaes the growth of fecal coliforms; can yeild colonies w/ green metalic sheen
Hektoen Enteric agar
selects for salmonella and shigella speices
inhibits gram + organisms; medium contains bile salts and crystal violet; colonies of lactose fermentors turn red
Manitol salt agar
selects for staphyloccoci; red medium turns yellow for pahtogenic organisms
serves as a growth control
phenyltheyl alchol agar
selects for gram + and inhibits gram - organims by inergering w/ DNA synthesis
what is the purpose of the durham tube?
why were there different types of phenol-red broths?
name one carbon source that was tested for its capacity to support bacterial growth?
sugras- lactose, glucose, sucrose and citrate
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
what chemical will you use to perform the catalse test?
what is the indicator that an organims is catalase +?