4 & 5 Flashcards
Negative strains and why used
simple strain in which organisms appear clear against a dark background. used to observe capsules or inclusion bodies. prevents eyestrain when many fields are stained. cells appear larger than they really are
what does streptococcus form
long fragile chains in broth but if they grow in a colony on a plate, it is sometimes difficult to make a smear with chains intact.
Wet mounts and hanging drop slides allow for viewers to see what
motility, form, viability
what can you see with staining, positive and negative
shape and grouping after cell division
what needs more light, wet mount or stained prep
stained prep, wet mount requires a low level of light to maximize contrast
how many um are in a mm
in a m
1000
10^6
differential stains
specifically stain certain morphological features
Gram stain what it does
reveals morphology and arrangment of cells. But also info about the cell wall
Gram positive stained with gram stain, what color is it and why
purple because they have thick cell walls of peptidoglycan
Gram negative stained with gram stain, what color is it and why
pink because they have thin cell walls of peptidoglycan.
order of dyes in gram stains
crystal violet, iodine, alcohol, safranin
iodine function
acts as a mordant, binds the dye to the cell
T/F gram-positive can appear gram negatives
true, by using too much alcohol
T/F gram negatives can appear gram positives
false
safranin uses
not essential, used as a way of dying the colorless cells so they contrast with the purple
