lab test 3 Flashcards
exoenzyme
outside cell
where is endoenzyme substrate?
inside cell
which enzymes are classified as hydrolytic reactions?
exoenzymes
subtrates of exoenzymes are soluble or insoluble
insoluble which causes watery medium to have an opaque appearance
exoenzyme subtrates (4)
- large
- polymer
- macromolecule
- insoluble
exoenzyme end products (3)
- small
- monomer
- soluble
what substances are present in the clear area around a streak of growth on a lipid plate? explain.
lipid hydrolysis took place and what is left on the clear area is the fatty acids, glycerols, and lipase enzymes.
would production of an endospore be catalyzed by an exo or endoenzymes?
endoenzymes because enzymes working inside of the cell create the spore
what does fermentation alwasy produce?
small, two or three carbon acids
what does fermentation sometimes produce?
- 2-3 carbon alcohols
- CO2 gas
- H2 gas
which group for which patterns of sugar fermentation is most useful to test?
facultative organisms - they ferment some sugars but not all since they also do respiration
what does the Durham tube do?
capture any CO2 gas produced during fermentation
what are the three sugars used to identify facultative enterics?
glucose, lactose, sucrose
what carbohydrate fermentation result would be labeled with A?
acid with no gad
what carbohydrate fermentation result would be labeled with AG?
acid with gas in Durham tube
staph will always be catalase ____
positive
strept will always be catalase ____
negative
what does MRSA stand for?
methicillin resistant staph. aureus
what does VRSA stand for?
vancomycin resistant staph. aureus
what does it mean for a bacteria to be hemolytic?
they rupture RBCs to eat the contents inside them
what commonly used bacteria in lab is hemolytic?
staph. aureus
strep is gram (?)
positive
what selective medium would you use if you suspect an organism is staph after a positive catalase test?
mannitol salt agar
what sugar do most pathogenic strains of staph. aureas ferment?
mannitol
how will the pH indicatior show positive mannitol fermentation?
change from red to yellow
what sets micrococcus apart from staph?
it has bright yellow colonies
what is the most definitive test for staph.a?
coagulase
why is mannitol fermentation not a definitive test for staph. aureus?
bc it is not the only bacteria that can ferment mannitol
which strep is the causative agent of strep throat?
pyogenes
if a catalase test is negative than it may be…
a gram pos. streptococcus
what does gamma hemolysis look like?
nothing changed
Lancefield group A:
- strep. pyogenes
- clear around A disk
Lancefield group B:
- strep. that colonizes vagina
- risk of spreading meningitis to newborns
Lancefield group D:
- strep pneumoniae
- clear around P disk
what is the clearing around drug disk called?
zone of inhibition
microaerophiles prefer…
- dec. in O2
- inc. in CO2
what are the red patches at the back of your throat when you have strep?
breakdown of red blood cells (hemolysis)
what are the white patches at the back of your throat when you have strep?
strep bacteria
how can the cytochrome oxidase test be useful if most bacteria have this enzyme anyways?
can be definitive if an organism lacks this enzyme
oxidase containing organisms are classified as ___?
aerobes
how do anaerobes remove hydrogen and and electrons frim carriers?
fermentation
what does SIM stand for?
sulfure indole motility
what does the SIM test detect?
- motility
- indole production
- H2S production
what kind of organism is the SIM test most useful for?
gram negative enteric rods
Interpret the SIM result: cloudiness throughout
- motile
- (-) for H2S production
Interpret the SIM result: black throughout
- motile
- (+) for H2S production
Interpret the SIM result: cloudiness along stab line
- non-motile
- (-) for H2S production
Interpret the SIM result: black along stab line
- non-motile
- (+) for H2S production
what does H2S react with to make black precipitate?
Fe
enzyme that breaks down tryptophan:
tryptophanase
end product of tryptophanase:
- indole
- pyruvate
- ammonia
how much glucose in TSIA?
~0.1%
how much lactose in TSIA?
~1.0%
how much sucrose in TSIA?
~1.0%
TSIA is used to differentiatie which kind of organisms?
facultative
where does respiration occur in TSIA?
slant portion only
what does glucose fermentation only look like in the tube?
red top yellow butt
what dye is used for the pH indicatior in TSIA?
phenol red
what does it look like if the organism ferments glucose + another sugar?
all yellow
what if the organism does not ferment sugar at all?
red top orange butt
which of the five reactions tested in TSIA would be undetectable if the glucose concentration was 1.0%?
- glucose only fermenters would be undetectable
- whole slant would be yellow
what are the five TSIA reactions?
- glucose fermentation
- multiple sugar fermentation
- CO2 production
- H2S production
- aerobic (respiration) + protein metabolism
what does IMViC stand for?
Indole
Methyl red
Voges-proskauer
Citrate
selective media
media that has toxins or dyes that inhibit the growth of some organisms but support the growth of others
enriched media
media supplemented with blood or other nutrients to allow growth of organisms that cannot grow on generic media
differential media
differentiates between dif types of organisms based on growth or color changes - Ex. on EMB lactose fermenters are dark purple or metallic green
E.Coli IMViC results
++–
order of IMViC results
indole test, methyl red, voges-proskauer, citrate
enterobacter IMViC results
–++
name for organisms that split glucose into pyruvate and ferment pyruvate into different acids
mixed acid fermenters
what pH do mixed acid fermenters produce and what does that result look like in a tube?
4.0 - red
what is unique about simmons citrate medium?
contains only INORGANIC nutrients such as NO3 and SO4
what is the only organic molecule in a citrate test?
citrate - so if an organism does not have citrase it cannot use it
what happens when CO2 combines with excess sodium in citrate test?
makes Na2CO3 which is basic
what is the pH indicator used in the citrate test?
brothymol blue
