Lecture 3 woohoo Flashcards
what is the most common way to isolate a pure colony
streak plate
What does indirect ELISA detect
Antibodies
what does direct elisa detect
antigens
bacteriophage
virus that only affects bacteria
What is agar
Media/food
the stuff on the plate to grow the bacteria
what is the purpose of resolving powder
allows you to see two different things as two different things
what is the structure of a gram positive bacteria
cell wall
thick peptidoglycan layer
what is the structure of a gram negative bacteria
Has 2 cell walls
thin peptidoglycan layer
what are the three ways to grow the bacteria
streak plate
pour plate
spread plate
How does a spread plate work
take a sample and dilute it into a bunch of different concentrations to eventually get a countable number
what was the first technique invented to isolate a pure colony
pour plate
How does a pour plate work
put a bit of sample in dish (blood)
add media
mix it
incubate it
what are two issues with the pour plate technique
Temperature can either be too hot/cold and damage bacteria or not be good enough to pour
bacteria can get stuck in media
what is the reason to heat fix when staining
denatures the proteins
allows bacteria to stick to sides as opposed to getting washed away
what two substances bind strongly to the peptidoglycan layer
crystal violet and iodine
what colour does the bacteria turn when the iodine and crystal violet binds with the peptidoglycan layer
purple
what happens if you heat fix too much
you just get a blob
why do we flood with pink dye
the gram negative would be invisible under a microscope otherwise
what colour is gram positive after staining
purple
What colour is gram negative after staining
pink
what kind of bacteria goes colourless after being washed with ethanol
gram negative
why does the gram negative look colourless after being washed w ethanol
ethanol will wash away the outer cell wall and peptidoglycan layer, which was what was stained
why does the gram positive not go colourless
the ethanol will only wash off part of the cell wall
does gram positive or gram negative have a thicker peptidoglycan layer
gram positive
if you have a thick peptidoglycan layer, how many cell walls do you have
1, you “sacrifice” a cell wall for a thicker peptidoglycan layer
what are the four types of media
chemically defined
chemically undefined
macconkey
selective differential
what is a chemically defined media
you can control every ingredient (quantities etc), could be made of glucose, sugar etc
what is a chemically undefined media
you cannot control every ingredient; exact amounts and kinds of nutrients are not known