L7 Flashcards
whats the purpose of a candle in a jar?
creates a low oxygen environment
what does a candle in a jar do regarding the gases
it reduces CO2 but will not fully remove O2 because candle will burn out before all O2 is used up
whats a pro to using a broth media?
con?
grow small to large quantities of culture
contamination AND growth causes cloudiness - not sure what is contaminating or what is growing because it all gets cloudy
whats a pro to using a plate media?
con?
easy to store - easy to see what happens to the plate
they are thin and not good for a long term - the nutrients on the media get used up fast
whats a pro to using a slant media (same media as plate)?
con?
provides more surface area than a regular tube
cannot isolate bacteria
whats a pro to using a semi solid deep media?
con?
bacteria can migrate from point of inoculation - look for motility
difficult to check for purity
where does Agar come from?
red algae
why didn’t gelatin plates work
they melted at too low temperatures and bacteria could digest them
when does Agar plate melt
85 degrees
is the basic plate (nutrient agar) selective
no
what is a nutrient agar suitable for
non-fastidious organsims
(non picky eaters)
what is a fastidious organisms
requires complex or particular nutrients to culture
what is a selective media
encourages the growth of some bacteria while preventing the growth of others
what is differential media
provides different visual cues as to the type of organism growing
what is required for a differential media to be successful
growth to differentiate the different bacteria
whats an enriched media
allows particular species to grow better
ie. rare bacteria to show up in a mixed bacteria
what kind of plate is macConkey Agar
selective and differential
what do macConkey Agar plates select against
non enteric gram positives
what does a macConkey Agar plate contain
lactose and pH indicators
what does the pH indicator do in macConkey Agar
gives it the pink/purple
gives the indicator of lactose fermentation
whats a lactose positive result of macConkey Agar plate
pink/purple
what colour do fermenters turn in macConkey Agar plate
purple
what grows on a macConkey Agar plate
gram (-)
what kind of plate is a Mannitol Salt Agar
selective and differential
what is a Mannitol Salt Agar made of?
Mannitol
salt (favours halophiles)
what does a fermenter turn on a Mannitol Salt Agar plate
yellow
what colour is a Mannitol Salt Agar
red
what is a Mannitol Salt Agar plate useful for detecting
staphylococcus aureus
what kind of plate is a blood agar plate
enrichment and differential
what is a blood agar plate made of
sheep blood
what is an alpha hemolysis
discolouration in or under the colony by bacteria that release H2O2 reducing Fe
what is beta hemolysis
clearing due to lysis of RBCs by bacterial enzymes
what is gamma hemolysis
no change
what plate tests for hemolysis
blood agar plate
what plate is not good for bacteria
Saboraud Dextrose Agar
what does a Saboraud Dextrose Agar plate contain
same as nutrient age but high amount of glucose
whats the pH of Saboraud Dextrose Agar
5.6
what does the sugar and acidic pH select for in Saboraud Dextrose Agar plates
yeasts and molds
what kind of diagnostic tube is a SIM deep
differential x3
what 3 things does SIM deep test for
sulfur reduction
indole production
motility
how to test for sulfur reduction in SIM deep tube
if H2S is produced it will react with ammonium iron II sulphate and turn black
how do test for indole production in SIM deep tube
by dripping kovaks reagent on top after incubation
if it turns red, it is positive for tryptophan
how to determine motility in a SIM deep tube
if cells grow away from the stab the cells are motile
whats the point of testing for indole in SIM deep tube
looking for a particular enzyme (tryptophan)
is the oxidase test a media?
no
what kind of infection does an armadillo carry
M. leprae
humans and ____________ carry M. leprae infections
armadillos
what is the oxidase test
add a complex reagent that if it reacts it tests for cytochrome 3 oxidase (purple = positive)
what is the biochemical identification system
doing several tests at once and then looking up scores in a booklet for species
what are 2 additional identification methods
DNA testing
Antibody testing
hoe long is mycobacterium leprae growth time
12-14 days
how fast can E coli divide
20 min
what is e coli weight
1 x 10^-12
why do we need to use a logarithmic graph when measuring bacteria growth
exponential growth of bacteria
will a cuvette get more cloudy as a bacteria growth occurs
yes
whats the appropriate amount of colonies to do dilution calculations with
25-250
what does a counting chamber count
cells but not live cells
whats the BEST number to get on a plate for cell count
100
why is 25-250 the good cell range?
because at both extremes the error is the same (equal accuracy)
