micro lab quiz #2 Flashcards
what is the most useful and widely used test in microbiogy lab
gram’s stains
how fast can gram stain give results
about 15 minutes
in grams stain what is purple
gram positive
in grams stain what is pink
gram negative
what are the color in gram stains due to
components in cell wall
purple has what kind of cell wall
thick
pink has what kind of cell wall
thin
the cell wall in gram positive bacteria is
90% peptidoglycan and 10% lipid
the cell wall in gram negative bacteria is
10% peptidoglycan and 90% lipid
gram stain procedure
crystal violet, iodine, alcohol, safranin
why doesn’t the gram negative keep crystal violet
cell wall too thin to capture it
why does iodine wash away the crystal violet in gram negative
peptidoglycan layer is thin
two ways to tell bacteria apart
shape and color they stain
why are gram positive easily treatable with antibiotics
they lack the outer phospholipid bilayer (plasma membrane
layers of gram positive bacteria
plasma membrane, thick cell wall, outer capsule,
layers of gram negative bacteria
plasma membrane, thin cell wall, plasma membrane, outer capsule
purpose of gram stain
identify type of bacteria
alcohol is what kind of chemical
destaining it has dehydrate nature
when you add alcohol what happens to gram positive
capsule goes away and cell wall shrinks
when you add alcohol what happens to gram negative
capsule and 2nd plasma membrane goes away and cell wall shrinks
gram negative loose their color because
it has such thin cell wall
circle shape
cocci
rod shaped
bacill
strep bacteria
chain
staph bacteria
cluster
strepbacillus bacteria
chain
exoenzyme test
starch and lipids
what can you see in exoenzyme tests
can see if an organism can break down large macromolecules that have been placed in the agar
what color does the iodine turn when added to the starch agar
black/blue
Absence of the blue-black color indicates
the starch is no longer in the medium
what shows a positive reaction for starch test
clear zone around bacteria
what does the clear zone in the starch agar indicate
starch has been removed in the area around the bacteria
starch hydrolysis
starch is broken down
starch tests have a bacterium that has a positive starch test possesses
3 enzymes that are needed to break down glucose and maltose (then can be transported into bacteria for energy production
iodine bonds with starch to
form a purple precipitate, iodine does not bond with glucose
exoenzymes
amylase lipase
hydrolyze
digestion by the addition of water
the lipid agar test is supplemented with
tributryin, a triglyceride (type of fat)
why is the starch agar opaque
addition of tributyrin
what is positive for starch agar test
zone of lipolysis
zone of lipolysis
organisms excreting lipase
lipid plate gets what kind of placement on the agar
thick streak
starch plate gets kind of placement on the agar
squiggly lines
selective agars
allow certain types of bacteria to grow while inhibiting the growth of other bacteria
what are two ways to make agars selective
making sure that that macromolecule is the only high quantity food source in an agar, adding dyes, antibiotics, or salt
what is a popular ph indicator
phenol red
what can metabolize mantel
s. aures
if ph is bellow 6.8
yellow
if ph is 7.4-8.4
red
if ph is 8.4 and above
hot pink
what is likely used when a staph infection is likely or possible
Mannitol Salt Agar
how does the mannitol salt agar select staphylococcus
addition of 7.5% salt
Eosin Methylene Blue Agar is used when what is suspected
E. coli or another generic gram negative rod
how does the EMB select gram negative rods
with addition of methylene blue
what acts like the ph indicator in EMB
eosin
what inhibits GPR in EMB
methylene
what is the food source for EMB
lactose
what is the food source for MSA
mannitol
action of MSA
selective and differential
action for EMB
selective and differential
action for BAP
not selective but differential
what is the enzyme that the bacterium must make for MSA
mannitol dehydrogenase MDH
in MSA what is end product if mannitol is broken down by microbe
ethanol
if EMB is black/green its
lactose postive
what is the enzyme needed to break down into galactose and glucose
lactase
what is the end product of the breakdown of lactose
lactic acid
why is BAP enriched with whole blood cells
certain bacteria produce enzymes capable of breaking down blood cells
what do BAP show
if bacteria are hemolytic or not
beta hemolysis
total breakdown of RBC
alpha hemolysis
breakdown of RBC but not hemogolbin
gamma hemolytic
growth but no breakdown of RBC
is starch selective/ differential
not selective but differential
is spirit blue selective/ differential
not selective but differential
what are the main agars you use for a specimen
BAP, MSA, EMB
colorless in starch plate means
starch is no longer there or positive
3 enterics
Baccillus subtilus, E. coli, L. lactis
if lipid plate turns blue to tan what does that mean
postive, fatty acid release
if the air around the colony does not change color there is no zone of hemolysis then
bacteria is considered lipid negative
when bacteria that ultilize sugars
they produce a lot of waste
when bacteria produce a lot of waste then
the ph drops
acidic waste is
flushed out of the bacteria into the agar
what happens if bacteria cant flush out waste
becomes a coffin
what kind of tests are sugar tests
differential
what kind of ph indicator does carbohydrate test have
phenol red
E. coli and Ptoteus hauseri are
GNR
L. lactis and Bacillus subtilis
GPR
in carb tests if it only had A then
it doesn’t need lipid or starch
catalase
breaks down hydrogen peroxide
in catalase test what indicates positive result
bubbling
in catalase test what indicates negative result
no bubble or very little
is pseudomonas aeruginosa catalase positive or negative
postive
S. aures catalase positive or negative
postive
E. coli catalase positive or negative
postive
Strep agalactiae catalase positive or negative
negative
