lab Flashcards
differential medium
ex
identification of organism by appearence or how ti changes medium during groth
(use an indicator)
ex: mannitol salt agar and macconkey
whats manniotl salt agar
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
whats Macconkey agar
selective and differential
- fermentation of lactose yeilds brick red colonies (differential)
- inhibits growth of gram pos bacteria bc bile salts? (selective)
whats selctive medium
ex
contains ing inhibitory to all but one microorganism
what is mitris salivarius agar
selective: Potassium tellurite and crystal violet which inhibits growth of gram + except streptococci
differential: sucrose
direct method to enumerate microbes
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
indirect method of enumerate imcrobes
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
describe light emitted by alivibrio
- bc of luciferase enzume and aoxidation/red rxn with FMNH2
- light only emitted when quorum is reached
swimming motility is ___ swarming is ____
swimming = unicellular and swarning = multicellular
*brownian motion = vibrating in place
how can you determine if microbes motile
semi-solid agar growth med with TTC redox dye
cells swim towds or away form soemthing via ___
taxis
- of stim = light then called phototaxis