lab

Question 1

differential medium

ex

Answer 1

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

(use an indicator)

ex: mannitol salt agar and macconkey

Question 2

whats manniotl salt agar

Answer 2

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

Question 3

whats Macconkey agar

Answer 3

selective and differential

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

Question 4

whats selctive medium

ex

Answer 4

contains ing inhibitory to all but one microorganism

Question 5

what is mitris salivarius agar

Answer 5

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

Question 6

direct method to enumerate microbes

Answer 6

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

Question 7

indirect method of enumerate imcrobes

Answer 7

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

Question 8

describe light emitted by alivibrio

Answer 8

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

Question 9

swimming motility is ___ swarming is ____

Answer 9

swimming = unicellular and swarning = multicellular

*brownian motion = vibrating in place

Question 10

how can you determine if microbes motile

Answer 10

semi-solid agar growth med with TTC redox dye

Question 11

cells swim towds or away form soemthing via ___

Answer 11

taxis

• of stim = light then called phototaxis