lab Flashcards

1
Q

differential medium

ex

A

identification of organism by appearence or how ti changes medium during groth

(use an indicator)

ex: mannitol salt agar and macconkey

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2
Q

whats manniotl salt agar

A

differential and selective

in differntial: fermentation of carbohydrate mannitol causes pH change - staphlococcus aureus produces yellow zone around colonie

as selective: 7.5% NaCl inhibits groth of gram - and gram pos except staphlococci

**ue to isolate gram pos like staph which is on skin

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3
Q

whats Macconkey agar

A

selective and differential

  • fermentation of lactose yeilds brick red colonies (differential)
  • inhibits growth of gram pos bacteria bc bile salts? (selective)
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4
Q

whats selctive medium

ex

A

contains ing inhibitory to all but one microorganism

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5
Q

what is mitris salivarius agar

A

selective: Potassium tellurite and crystal violet which inhibits growth of gram + except streptococci
differential: sucrose

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6
Q

direct method to enumerate microbes

A

Petroff-Hausser chamber: dilution of cell spention placed on special slide with grid, count number in a small volume and extrapolate

Electronic particle counter (coulter counter): non conudcting particles like cells cause inc resistance proportional to volume when passing thru electronic feilds

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7
Q

indirect method of enumerate imcrobes

A

membrane filtration: cell sus drawn through mem, large cells excluded then place that membrane on nutrient medium and incubate til colonies form (1 colony = 1 cell and consider dilution factor)

Most probable number (MPN) method: statistical, incoluble tubes with culture media of several dilutions of cell suspention and record # of pos and neg responses of growth - estimatedensity according to a table

Viable plate counts (std palte count): use spread or pour plate and count CFU then extrapolate back

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8
Q

describe light emitted by alivibrio

A
  • bc of luciferase enzume and aoxidation/red rxn with FMNH2
  • light only emitted when quorum is reached
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9
Q

swimming motility is ___ swarming is ____

A

swimming = unicellular and swarning = multicellular

*brownian motion = vibrating in place

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10
Q

how can you determine if microbes motile

A

semi-solid agar growth med with TTC redox dye

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11
Q

cells swim towds or away form soemthing via ___

A

taxis

  • of stim = light then called phototaxis
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